Today I’m sharing this classic Boston cream pie, with layers of buttery high altitude yellow sponge cake, vanilla bean custard, and chocolate ganache. If you’re not familiar with a Boston cream pie, it’s actually not a pie at all, but a cake with a cream or custard filling, and it’s the official dessert of Massachusetts. This dessert dates back to the 1800s, when cakes were often baked in pie pans, so the terms “cake” and “pie” were often used interchangeably. But it’s delicious either way.
You might also love this chocolate fudge cake with ganache, white velvet cake, and red velvet cake with cream cheese buttercream.
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Why You’ll Love This Recipe
Elegant and Classic. I love a good classic cake recipe, and this cake has so many good things going on. The soft, buttery cake, creamy custard and rich chocolate ganache makes a delicious dessert that’s hard to stop eating.
Easy to Make. Okay, so I know there are three elements to this cake, but honestly, it comes together quickly without much fuss.
High Altitude Tested. I develop all the recipes on my site for Denver’s altitude of 5,280 feet. If you’re at a lower or higher elevation, please see my FAQs for guidance on adjusting recipes for your altitude.
See the recipe card at the end of the post for the full ingredients list and instructions.
Ingredients
Cake
- Butter + Oil. A combination of melted butter and vegetable oil adds fat, flavor and moisture.
- Sugar. Granulated sugar adds sweetness and moisture.
- Eggs. Gives the cake strength and adds richness.
- Vanilla Extract. Flavor.
- Buttermilk + Sour Cream. A combination of buttermilk and sour cream adds moisture, fat and acidity, for a soft, tender cake crumb.
- Cake Flour. Gives the cake structure and strength. If you don’t have cake flour, you can also use all-purpose flour.
- Baking Powder. Leavens the cake, making it rise as it bakes.
- Salt. Balances the sweetness.
Custard
- Sugar. Sweetens the custard.
- Corn Starch. Thickens the custard so that it can support the weight of the top cake layer.
- Milk. Use whole milk for a more flavorful custard.
- Egg Yolks. Add richness and flavor.
- Vanilla. Use a good quality vanilla extract, or the seeds scraped from a vanilla bean for the best flavor and pretty specks of vanilla. You can also use vanilla bean paste.
- Butter. After cooking the custard, a little butter adds richness and flavor.
Ganache
- Chocolate. Good quality dark chocolate (between 55-60% cacao) will make the best chocolate ganache.
- Cream. Be sure to choose heavy whipping cream, not half and half or table cream.
TIP: It’s best if your cake pans are 3 inches deep, as there’s almost too much batter to bake in 6 inch pans that are only 2 inches deep. The shallower pans will still work (it’s what I used), but the top of the cake will brown a little bit more than if you use deeper pans. You can also use 8-inch pans instead, for thinner cake layers.
Instructions
Cake
- Preheat the oven to 350 F, and spray the bottoms of two 6-inch cake pans with non-stick baking spray.
- In a large bowl, whisk together the melted butter, oil, sugar, eggs, vanilla, buttermilk and sour cream, until smooth.
- In a separate bowl, sift together the flour, baking powder and salt. Add the dry ingredients to the wet, and whisk for 10-15 seconds until smooth and well combined.
- Divide the batter between the pans. Bake on the center oven rack for about 25-27 minutes, until a cake tester comes out clean.
- Set the pans on a cooling rack, cover loosely with a clean kitchen towel, and cool completely before assembling your cake.
Custard
- When your cakes are cool, and you’re ready to assemble the cake, you can make the pastry cream.
- In a saucepan, whisk together the sugar and corn starch. Slowly whisk in the milk, then the egg yolks, until smooth.
- Cook the custard over medium heat, whisking constantly. As the custard starts to thicken, it may seem lumpy or curdled at first, but just keep whisking and it will smooth out. When the custard has thickened, continue to cook and whisk for 1 minute, to fully activate the corn starch. This whole process should take about 8-10 minutes.
- Remove from the heat and vigorously whisk in the vanilla and butter until smooth. The custard will be thick, and you don’t need to wait long for it to cool to assemble your cake.
TIP: If the custard seems too thick for your liking, you can whisk in some cold milk or cream, 1 tablespoon at a time, whisking vigorously until smooth. If the custard is too soft, though, it won’t be able to support the weight of the top cake layer without squishing out the sides.
- Remove the cakes from the pans, and set one cake on a cake plate or pedestal. Spread the warm custard in an even layer over the cake, stopping at the edges, or fill a piping bag with the custard and pipe it onto the cake.
- Set the second cake on top of the custard, and gently press it down a little, but not so much that you squish the custard out the sides.
Ganache
- Finely chop the chocolate, scrape into a bowl, and set aside.
- Warm the cream in the microwave or in a saucepan on the stove, just until it begins to simmer around the edges.
- Pour the hot cream over the chocolate and stir until smooth and shiny.
- Let the ganache cool at room temperature for 10-20 minutes, stirring occasionally, until it’s thick enough that it won’t run off the top of the cake. Pour the ganache over the cake, gently spreading it towards the edges so it just starts to drip over the edges, but doesn’t run down the sides of the cake.
- You can serve the cake immediately, or let the ganache set for about 30 minutes first.
Be sure to read all of my BAKING FAQs where I discuss ingredients, substitutions and common questions with cake making, so that you can be successful in your own baking! I also suggest reading these comprehensive posts on making Perfect American Buttercream, How to Stack, Fill, Crumb Coat and Frost Layer Cakes and How to Use Piping Bags.
Frequently Asked Questions
Is custard the same thing as pastry cream?
Yes, custard and pastry cream are pretty much the same thing. I have a post just on making vanilla custard. You’ll note that I made the custard much thicker for this Boston cream pie, so that it can support the weight of the top cake layer.
What kind of chocolate did you use for the ganache?
I used Chocolove 55% dark chocolate, which I love both for baking and eating. It’s creamy and just sweet enough without being too bitter. In general, you shouldn’t use chocolate chips when making ganache, since they don’t melt as smoothly.
What if I don’t have 6-inch cake pans?
This recipe makes two thick 6-inch cake layers, but you can also bake the cake batter in two 8-inch cake pans for thinner cake layers. For your 6-inch pans, it’s best to use pans that are 3 inches deep.
Can I double this recipe for a larger cake?
Yes, if you double the recipe, you should bake the cake in two 9-inch cake pans.
Should Boston cream pie be refrigerated?
Since the custard is perishable, you should refrigerate the assembled cake in an airtight container to keep the naked cake layers from drying out.
Can I make the cake, custard or ganache in advance?
You can make the cake layers in advance, wrap them well in plastic wrap, and freeze them for up to3-6 months. For the pastry cream, I advise only making it when you’re ready to assemble your cake. The ganache cannot be made in advance, as it needs to be poured on top of the cake while it’s warm. Keep in mind that since the cake layers are “naked”, they will dry out faster than a cake that’s covered in buttercream.
How long does this cake stay fresh?
Boston cream pie is best eaten within 2 days.
Is this a high altitude cake recipe?
Yes, I develop all of my recipes for Denver’s high altitude of 5,280 feet.
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High Altitude Boston Cream Pie
All recipes on Curly Girl Kitchen are developed for high altitude at 5,280 feet. See FAQs for adjusting to higher or lower elevations.
Equipment
- 2 6-inch Round Cake Pans (3 inches deep)
- Saucepan + Whisk
Ingredients
Cake
- 6 tbsp unsalted butter, melted
- 2 tbsp vegetable oil
- 1 cup granulated sugar
- 2 large eggs
- 1 tsp vanilla extract
- ⅔ cup whole buttermilk
- ⅓ cup full-fat sour cream
- 1 ½ cups cake flour, spooned and leveled
- 1 ¾ tsp baking powder
- ½ tsp coarse Kosher salt (if using table salt, use half the amount)
Custard
- ⅓ cup granulated sugar
- 3 tbsp corn starch
- 1 cup whole milk
- 3 large egg yolks
- 1 tsp vanilla bean paste (or the seeds scraped from 1 vanilla bean)
- 2 tbsp unsalted butter
Ganache
- 2 oz semi sweet or dark chocolate, finely chopped
- 1 ½ oz heavy whipping cream
Instructions
Cake
- Preheat the oven to 350 F, and spray the bottoms of two 6-inch cake pans with non-stick baking spray.TIP: It's best if your pans are 3 inches deep, as there's almost too much batter to bake in 6 inch pans that are only 2 inches deep. The shallower pans will still work (it's what I used), but the top of the cake will brown a little bit more than if you use deeper pans.
- In a large bowl, whisk together the melted butter, oil, sugar, eggs, vanilla, buttermilk and sour cream, until smooth.
- In a separate bowl, sift together the flour, baking powder and salt. Add the dry ingredients to the wet, and whisk for 10-15 seconds until smooth and well combined.
- Divide the batter between the pans. Bake on the center oven rack for about 25-27 minutes, until a cake tester comes out clean.
- Set the pans on a cooling rack, cover loosely with a clean kitchen towel, and cool completely before assembling your cake.
Custard
- When your cakes are cool, and you're ready to assemble the cake, you can make the pastry cream.
- In a saucepan, whisk together the sugar and corn starch. Slowly whisk in the milk, then the egg yolks, until smooth.
- Cook the custard over medium heat, whisking constantly. As the custard starts to thicken, it may seem lumpy or curdled at first, but just keep whisking and it will smooth out. When the custard has thickened, continue to cook and whisk for 1 minute, to fully activate the corn starch. This whole process should take about 8-10 minutes.
- Remove from the heat and vigorously whisk in the vanilla and butter until smooth. The custard will be thick, and you don't need to wait long for it to cool to assemble your cake.TIP: If the custard seems too thick for your liking, you can whisk in some cold milk or cream, 1 tablespoon at a time, whisking vigorously until smooth. If the custard is too soft, though, it won't be able to support the weight of the top cake layer.
- Remove the cakes from the pans, and set one cake on a cake plate or pedestal. Spread the warm custard in an even layer over the cake, stopping at the edges, or fill a piping bag with the custard and pipe it onto the cake.
- Set the second cake on top of the custard, and gently press it down a little, but not so much that you squish the custard out the sides.
Ganache
- Finely chop the chocolate, scrape into a bowl, and set aside.
- Warm the cream in the microwave or in a saucepan on the stove, just until it begins to simmer around the edges.
- Pour the hot cream over the chocolate and stir until smooth and shiny.
- Let the ganache cool at room temperature for 10-20 minutes, stirring occasionally, until it's thick enough that it won't run off the top of the cake. Pour the ganache over the cake, gently spreading it towards the edges so it just starts to drip over the edges, but doesn't run down the sides of the cake.
- You can serve the cake immediately, or let the ganache set for about 30 minutes first.
Definitely was not as pretty as yours. For a first time make, it wasn’t to bad.
I found your website while searching for whether altitude affects pastry cream. I was thinking that cornstarch needed to get to a certain temperature that would make it difficult at high altitudes. Is it based on liquid boiling rather than getting to a specific temperature? Having found your site just today, I’m excited to read through!
Wendy, I’ve never checked the temperature of pastry cream or pie filling, or other types of things that I thicken with corn starch. The corn starch is activated by heat, which is why it’s important to continue cooking it for a full minute after the mixture comes to a boil, to ensure the corn starch is fully activated.
I followed recipe exactly not over mixing etc. and it still fell in the middle. What could have been the problem?
Are you talking about the cake or the custard? What altitude are you at?
I love your cakes and cake design! This looks yummy! Can’t wait to try it. Just wondered if i wanted to make a bigger version of this cake (e.g. same height layers but 8inch pan) if i could simply multiply the cake ingredient quantities by 1.5 say? Would that work do you think? Thanks so much 😊
I would double the recipe for an 8-inch cake. If I recall, there are a few comments in the comments section from others who have made a larger version.
Made this using an 8″ pan, doubled the custard and the ganache. Fabulous!
Exquisite! I will always consult Curlygirl before any other recipe. The best cake, custard and ganache I’ve ever tried. Using real vanilla bean is well worth the cost. I’m a chocolate lover, so next time I’ll double the ganache.
Such a nice comment, thank you! 🙂
Made it for a birthday and it was delicious! Everyone loved it and it actually looked pretty good. I did have some trouble with the cake coming out of the pan, but in the end it worked out. I did use a 8” x 1.5” deep pan, so I had to double the ganache.
Hi there! Looks amazing and delicious. 😉 I plan on making this for my wife’s birthday coming up.
Did you “shave” the cakes to get that open sponge, clean look? If you did, what did you use for the job? I figure a fine cheese grater would do the trick, no?
Thank you! Love this site and your beautiful creations. 🤗
No, I don’t do that. If the cake’s crust has an uneven color, with some areas more brown than others, I might lightly rub off the darker bits of crust with my fingers, but that’s it. I hope your wife loves the cake!
Stunning and delicious! I used 2 8” cake pans. You get thinner cake layers with more surface for custard and ganache. I doubled the custard and ganache. Fantastic recipe!!
The cake was ok, not my favorite. The custard filling was so thick that it tasted funny. I did thin it out but it still had a cornstarch flavor to me. I wasnt interested in piping the filling, so a different recipe would be better for me next time.