Prague Cake: A Chocolate Cognac Cake

CakePreheat the oven to 350°F. Line a 9-inch springform or cake pan (at least 3 inches deep) with a round of parchment paper. Lightly grease only the paper with the oil.

In a bowl, combine the flour, cocoa powder, 1 Tbsp. of the sugar, and the baking powder. Sift together three times.

In a stand mixer fitted with the whisk, whip the egg whites and salt on medium speed until the egg whites resemble a thick, dense white foam, 1 1/2 to 2 minutes. With the mixer still running, gradually add the remaining 3/4 cup sugar a few tablespoons at a time. Continue to beat until the whites are thick, glossy, and opaque and hold stiff peaks, 3 to 5 minutes. Add the egg yolks one at a time, beating well after each addition. Slowly stream in the oil, mixing until fully incorporated.

Sprinkle one-third of the sifted flour mixture onto the batter and use a rubber spatula to gently but confidently fold it by hand until combined. Repeat with the rest of the flour mixture in two batches, being careful not to deflate the batter.

Gently guide the batter into the prepared pan and smooth out the top. Run a toothpick in a spiral motion, starting from the center and working your way out, to pop any large air bubbles.

Bake, without opening the oven door, until the cake springs back when pressed in the center and a tester comes out clean, 35 to 40 minutes.

Let it cool in the pan for 20 minutes. Run a paring knife between the edges of the cake and the pan to help release the cake and transfer to a wire rack to cool completely. Well wrapped, the cake will keep at room temperature for up to 2 days or up to 1 month in the freezer.

Cognac SoakIn a small saucepan, combine the water and sugar. Bring to a simmer over medium heat, stirring to help dissolve the sugar. Remove from the heat and add the Cognac. Set aside and allow to cool completely.

ButtercreamIn a heavy-bottomed medium saucepan, whisk together the egg yolks and water. Add the sweetened condensed milk and mix to combine. Heat over medium-low and cook, whisking constantly, until the custard thickens to the consistency of sweetened condensed milk straight from the can and starts to bubble, 8 to 10 minutes (an instant-read thermometer will read between 195°F and 200°F). Sift in the cocoa powder and salt, add the vanillin, and whisk to combine. Set aside to cool to room temperature.

In a stand mixer fitted with the whisk, beat the butter on medium-high speed until very light and fluffy, scraping down the bottom and sides of the bowl periodically, 4 to 5 minutes. Reduce the speed to medium and add the cooled custard a big dollop at a time, beating to fully incorporate and scraping down the bowl as needed. Add the Cognac and mix to combine. Use right away or keep at room temperature in an airtight container for 1 day or in the refrigerator for up to 1 month.

Assemble the Prague cakeCut the domed center off the top to even the cake out. Cut the cake horizontally into 3 even layers. Reserve the bottom layer for the top of the cake.

Place one of the other cake layers on a cake stand or plate. Brush the cake with 1/4 cup of the Cognac soak. Add 1/4 cup of the apricot jam, slightly warmed, and spread it evenly. Top with a generous 1 3/4 cups of the buttercream and use an offset spatula to spread it into an even layer. Center a second cake layer over the first and press it down gently to secure it. Repeat with the soak, jam, and buttercream. Nestle the reserved bottom layer, flat-side up, on top. Brush with 1/4 cup Cognac soak.

Warm the last of the jam again and strain through a fine-mesh sieve to remove any fruit pieces. Spread the strained apricot jam evenly over the top. Use the remaining buttercream to spread a very thin crumb coat over the sides to fill any gaps. (You will have some buttercream left over. Pair it with leftover cake scraps and soak for a chef’s snack!)

Refrigerate the cake until the jam no longer feels sticky to the touch and the buttercream is set, 3 to 4 hours.

GlazeBring 1 inch of water to a bare simmer in a medium pot over medium-low heat. In a heatproof bowl (that can sit over the pot of simmering water without touching the water), combine the chocolate, butter, corn syrup (if using), and salt and set over the pot. Stir occasionally to encourage melting and prevent the chocolate from burning. Once the mixture has melted and become smooth and glossy, remove from the heat. Allow to cool until it’s about body temperature, 10 to 15 minutes, before glazing.

To glaze the cake, set it on a wire rack set over a baking sheet lined with parchment paper. Pour the glaze onto the center of the cake, and, working quickly, use an offset spatula to spread it across the top in an even and thin layer and to push the excess over the sides. Cover the sides completely.

If desired, rewarm excess glaze from the baking sheet and decorate the top with chocolate piping.

Refrigerate for 5 to 6 hours or overnight to allow the flavors to meld. Bring to room temperature at least 2 hours before serving. Refrigerated, the cake will last for 3 to 4 days.