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Chocolate truffle cake on a marble and wood cake stand.

High Altitude Chocolate Truffle Cake

Heather Smoke
Six layers of moist chocolate cake are filled with creamy homemade chocolate custard, then covered in dark chocolate ganache and mini chocolate chips.

All recipes on Curly Girl Kitchen are developed for high altitude at 5,280 feet.

5 from 3 votes
Prep Time 45 mins
Cook Time 35 mins
Chilling Time 8 hrs
Total Time 9 hrs 20 mins
Course Dessert
Cuisine American
Servings10

Equipment

  • 6-inch Round Cake Pans (x3)

Ingredients
 

Cake

  • 1 cup all-purpose flour, spooned and leveled
  • ¾ cup + 2 tbsp granulated sugar
  • 6 tbsp unsweetened Dutch-processed cocoa powder
  • ¼ tsp baking powder
  • ½ tsp baking soda
  • ½ tsp coarse Kosher salt (if using table salt, use half the amount)
  • 2 large eggs, lightly beaten
  • ½ cup whole milk, room temperature
  • ½ cup sour cream, room temperature
  • ½ cup vegetable oil
  • 1 ½ tsp vanilla extract
  • ½ tbsp espresso powder (optional)

Custard

  • 4 tsp unsweetened Dutch processed cocoa powder
  • 1 tbsp granulated sugar
  • 4 tsp corn starch
  • 1 cup whole milk
  • 1 egg yolk
  • 1 tbsp unsalted butter
  • ½ tsp vanilla extract
  • 1 ½ oz good-quality dark chocolate, chopped (Chocolove Dark Chocolate, 55% cacao)

Ganache & Chocolate Chips

  • 4 oz (1/2 cup) heavy whipping cream
  • 4 oz good-quality dark chocolate, chopped (55% cacao)
  • 10 oz (1 bag) semi-sweet mini chocolate chips

Piped Ganache Frosting

  • 6 oz (3/4 cup) heavy whipping cream, divided
  • 4 oz good-quality dark chocolate, chopped (55% cacao)
  • ¾ cup powdered sugar
  • ¼ cup unsweetened Dutch-processed cocoa powder

Instructions
 

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.

Custard

  • The custard will need to be made at least 6 hours in advance (or overnight), so it has time to chill.
  • 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.

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.

Piped Ganache Frosting

  • This last step is optional, but the piped frosting adds a nice decorative touch. You can get the ganache for the frosting ready at the same time that you make the ganache for covering the cake, so that it's ready by the time you need it to decorate your cake.
  • 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.
    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.

Notes

The cake should be stored in an airtight container or cake carrier, for up to 3 days.  Keep the leftover cake refrigerated overnight, but bring it to room temperature for serving.
Keyword Chocolate Cake, Chocolate Truffle, High Altitude
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