High Altitude Chocolate Truffle Cake

Today’s high altitude chocolate truffle cake is for serious chocolate lovers only. There are six layers of moist chocolate cake, filled with creamy homemade chocolate custard. All that custard-soaked cake is then covered in dark chocolate ganache and mini chocolate chips.  Since there’s no buttercream, this cake is rich and dark, without being too sweet, making it a true celebration of chocolate.

This is also a surprisingly easy cake to make and assemble. While there are a few components, the cake, ganache and custard all come together quickly. Most of the time required to make this cake is simply spent waiting for the custard and ganache to cool so you can assemble the cake. And in today’s post, I’ve included lots of photos with step-by-step instructions to guide you as you make your own cake.

Looking for more chocolate recipes? You’ll love my double Dutch dark chocolate ice cream, flourless chocolate cake, and chocolate almond tart.

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What is a Chocolate Truffle Cake?

A chocolate truffle is a type of chocolate candy that’s usually made of ganache (heavy whipping cream + chocolate). The chilled ganache is rolled into balls and then coated in sweetened cocoa powder or melted chocolate. Chocolate truffles are dark, rich and not very sweet. In fact, they’re only as sweet as the chocolate used to make them. So if you use chocolate with 40-45% cacao, then your truffles will be sweeter than if you use chocolate with 55-65% cacao.

A chocolate truffle cake has all the flavors and textures of a chocolate truffle, in a decadent, show-stopping chocolate dessert that’s perfect for any holiday, birthday or other special occasion. In today’s cake you get soft, fluffy chocolate sour cream cake, creamy chocolate custard, and rich ganache. The texture of the chocolate chips is just delicious with all the creamy layers of cake and custard.

This chocolate truffle cake has three main components, the cake, the custard and the ganache. It’s a long list of ingredients and a lot of steps, but it really makes such a fantastic chocolate cake for a special occasion.

See the recipe card at the end of the post for the full ingredients list and instructions.

Ingredients

Chocolate Cake

The cake itself is my high altitude chocolate cake, which is my absolute favorite chocolate cake recipe.  I’ve made it dozens of times, and it never lets me down.  It’s soft, moist and rich, and it’s truly the best chocolate cake ever.  It’s so good, that I would happily eat it on its own without buttercream, or just with a little whipped cream and fresh berries.

• Dry Ingredients: all-purpose flour, granulated sugar, Dutch-processed cocoa powder, baking powder, baking soda, salt, espresso powder
• Liquid Ingredients: eggs, milk, sour cream, vegetable oil, vanilla extract

Chocolate Custard

I make my homemade chocolate custard – or pudding, if you like – with both cocoa powder and good-quality dark chocolate.  The custard is rich with whole milk and egg yolks, lightly sweetened with sugar, and finished with a little butter and vanilla extract.  I’ve used this same recipe to fill chocolate cream pies, or just to spoon into trifle bowls, layered with whipped cream.

When spread between the layers of cake, the custard soaks into the cake, creating an impossibly soft and moist chocolate cake, that stays fresh and moist for days and days.

Chocolate Ganache

Ganache is nothing more than chocolate + heavy whipping cream. You’ll be warming the cream, then pouring it over the chopped chocolate until it melts. Ganache is a delicious alternative to a traditional buttercream frosting.

TIP: The cakes can be baked one day in advance, wrapped tightly in plastic wrap after cooling.

Instructions

Bake and cool the chocolate cake.

• Preheat the oven to 350 F, and position a rack in the center of the oven.  Prepare three 6-inch cake pans by spraying the bottoms of the pans with non-stick spray.  After the cakes are cooled, you’ll be splitting each cake, for a total of 6 cake layers.
• In a large bowl, sift together the flour, sugar, cocoa powder, baking powder, baking soda and salt.  Add the eggs, milk, sour cream, oil, vanilla and espresso powder, and whisk well to combine.

• Divide the batter evenly between the pans, and bake the cakes for about 20 minutes, until a toothpick comes out clean, and the tops spring back when lightly touched.  Place on a cooling rack, cover loosely with a clean kitchen towel and let cool completely.

TIP: The custard will need to be made at least 6 hours in advance, so it has time to chill.

Cook and chill the custard.

• In a saucepan, whisk together the cocoa powder, sugar and corn starch.  Slowly whisk in the milk, then the egg yolks, whisking until smooth.
• Cook over medium heat, while whisking constantly, until the custard starts to thicken and bubble (this should take about 8-10 minutes). Once it starts to thicken, continue to cook for 1 full minute.
• Remove from the heat and whisk in the butter, vanilla and chocolate until smooth.
• Pour into a bowl, cover with plastic wrap resting right against the surface of the custard, and chill for at least 6 hours, or overnight.

TIP: The ganache will need to be made no more than one hour before you plan to assemble your cake – it needs to be slightly cooled, but still pourable.

Ganache

• The ganache will need to be made no more than one hour before you plan to assemble your cake – it needs to be slightly cooled and thickened, but still pourable.
• In a saucepan, heat the cream over medium heat just until it begins to bubble.
• Meanwhile, chop the chocolate and place in a bowl.

• Pour the hot cream over the chocolate, let stand at room temperature for 3 minutes, then stir with a spatula until smooth and thick.
• Set aside to cool for about an hour before assembling your cake.

Assembly

• Take the chilled custard and stir it up to loosen it slightly.
• Use a sharp knife to split the 3 cakes so you have 6 layers.
• Place one of the cakes, split side facing up, on a cake board or cake pedestal. Use a small offset spatula to spread 1/5 of the custard evenly over the cake, stopping 1/2 inch from the edge. Repeat stacking and filling the cakes with custard. You’ll have 6 layers of cake, filled with 5 layers of custard. For the final cake layer on top, set it on the cake with the split side facing down.

• Your cake layers may not look perfectly even, and that’s okay, since it’s difficult to spit cakes evenly. If the sides of the cake are too uneven, you can trim them a little with a sharp knife for straight up and down sides.
• To cover the cake in ganache, start by pouring about 1/2 of the ganache on top of the cake. Use a small offset spatula to nudge it towards the edges, then spread it evenly around the sides of the cake. Pour on the rest of the ganache, and finish spreading it evenly all over the cake.

• Before the ganache firms up, press handfuls of the mini chocolate chips around the sides and on top of the cake.  Scoop up any that fall and keep pressing them onto the cake until it’s fully covered.

TIP: This last step is optional, but the piped frosting adds a nice decorative touch. Since the ganache will need to chill for 1 hour, you can get it ready at the same time that you make the ganache for covering the cake. This way, it’ll be ready by the time you need it to finish decorating your cake.

Piped Ganache Frosting

• In a saucepan, heat 4 oz of the cream (1/2 cup) over medium heat just until it begins to bubble.
• Meanwhile, chop the chocolate and place in a bowl.  Pour the hot cream over the chocolate, let stand at room temperature for 3 minutes, then stir with a spatula until smooth and thick.
• Refrigerate the ganache for 1 hour, stirring it every 15 minutes so that it cools evenly. When it’s thickened and cooled completely, it’s ready to whip into frosting.
• To the cooled ganache, add the powdered sugar and cocoa powder. Use an electric mixer to whip the frosting for several minutes until fluffy and spreadable, adding the remaining 1/4 cup cream as needed, if the frosting is too thick.
• Fit a piping bag with tip 6B and fill with the frosting. Pipe decorative swirls on top of the cake.

TIP: Make sure the chocolate chips on top of the cake are pressed into the ganache. If you have any loose chocolate chips scattered on top, they will prevent the frosting from sticking.

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

Can I bake the cake in two 6-inch pans instead of three pans?

If your pans have a 3-inch depth, then you can probably divide the batter between two pans and bake the cakes without them overflowing. I haven’t tested this, though. But while it’s easy to split three cakes into six layers, it would be much more difficult to split two cakes into six layers. The best option would be to bake 2/3 of the batter in your two pans, then when you can free up a pan, bake the remaining 1/3 of the batter.

How should I adjust the recipe for a larger cake?

You can double this recipe and bake it in three 8-inch cake pans.

Will this recipe work if I don’t live at high altitude?

Since this is a high altitude chocolate cake recipe, you may need to make a few slight adjustments to the cake ingredients, such as decreasing the flour by several tablespoons, and increasing the leavening by 1/4-1/2 teaspoon. I suggest reading this article on high altitude baking adjustments.

What kind of chocolate do you use in the ganache and custard?

In both the ganache and the custard, I used Chocolove 55% Dark Chocolate. You can also use semi-sweet chocolate chips, but they don’t melt quite as smoothly as good-quality chocolate.

What’s the difference between chocolate cake and chocolate truffle cake?

Chocolate cake is assembled more simply with chocolate buttercream. A chocolate truffle cake is made of chocolate cake layers filled with custard, then covered in ganache and chocolate chips.

What if I can’t find mini chocolate chips to cover the cake?

You really need to use mini chocolate chips, since their small size works best for covering the cake. If you can’t find any, you can finely chop several bars of chocolate instead. If using chopped chocolate, refrigerate it for several minutes first, and press it onto the cake quickly, so the heat of your hand doesn’t melt the chocolate.

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