Ingredients for the ganache
1/2 cup (120 ml) heavy cream
2 tablespoons unsalted butter
2 tablespoons corn syrup
8 ounces (225 g) bittersweet chocolate, finely chopped
Ingredients for the raspberry buttercream
5 egg whites, at room temperature
1 cup (200 g) granulated sugar
1 pound (455 g) unsalted butter, softened
1/4 cup (60 ml) smooth raspberry preserves
Ingredients for the assembly
1 cup (240 ml) smooth raspberry preserves
1 pint (250 g) fresh raspberries
Method for the vanilla layers
Preheat the oven to 350° (175°C). Prepare three 10-inch (25-cm) round cake pans by lining the bottom of each with a round of parchment paper and spraying with nonstick baking spray.
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and granulated sugar until light and fluffy. Scrape down the sides and bottom of the bowl. Add the eggs, one at a time, scraping the bowl after each addition and making sure that each egg is completely incorporated before adding the next. Add the vanilla bean paste and mix.
In a bowl, whisk together the flour, baking powder, and salt.
Add one-third of the flour mixture to the egg-butter mixture and mix until just incorporated. Add half of the buttermilk and mix until just incorporated. Continue alternating additions of flour and buttermilk until both are fully incorporated.
Divide the batter evenly among the three prepared pans. Bake for 45 minutes, or until the tops of the cakes are golden brown and spring back when touched. Set aside to cool completely.
Method for the flourless chocolate layers
Preheat the oven to 325° (165°C). Prepare three 10-inch (25-cm) round cake pans by lining the bottom of each with a round of parchment paper and spraying with nonstick baking spray.
In the bowl of a stand mixer fitted with the whisk attachment, add the granulated sugar, cocoa powder, and salt and whisk together until well integrated. Add the eggs, one at a time, and mix until a smooth paste forms.
In a heatproof bowl, combine the chocolate and butter and place over a bain marie (a large saucepan half filled with gently simmering water). Stir with a large rubber spatula until the chocolate is completely melted.
With the mixer running on low speed, slowly pour the chocolate-butter mixture into the egg mixture, scraping all the chocolate into the bowl. Add the vanilla bean paste. Whisk until fully combined.
Divide the batter among the three prepared pans. Bake for 15 to 20 minutes, until the cake just begins to pull away from the sides of the pan and feels firm but not hard in the center. Set aside to cool completely.
Method for the ganache
In a saucepan, combine the cream, butter, and corn syrup. Bring to a simmer.
Place the chocolate in a heatproof bowl and pour the hot cream mixture over the chocolate, making sure the chocolate is completely covered. Allow to sit undisturbed for 2 minutes. Stir clockwise until the ganache is shiny and emulsified. Cover with plastic wrap and allow the ganache to cool just to a spreadable consistency.
Method for the raspberry buttercream
In the bowl of a stand mixer fitted with the whisk attachment, add the egg whites. Beat until just frothy.
Meanwhile, in a saucepan, combine the granulated sugar with cup (80 ml) water. Stir over medium heat until the sugar is completely melted. Attach a candy thermometer to the side of the saucepan and bring the syrup to 240°F (116°C).
With the mixer running on medium speed, slowly pour the hot syrup down the side of the bowl into the egg whites. Increase the speed to high and whip until stiff peaks form and the bowl is cool to the touch.
Add the butter, a few pieces at a time (you may not need it all). When the buttercream starts to look like it's curdling, add just one more piece of butter and continue whisking for a few minutes until the texture becomes smooth and creamy. Add the raspberry preserves and whisk until integrated.
Place a vanilla layer on a serving platter. Spread 3 tablespoons preserves evenly over the layer. Refrigerate for 10 minutes to set. Spread a very thin layer of ganache, about inch (3 mm) thick, along the top of the preserves. Top with a layer of chocolate cake and press gently to adhere. Spread a ¼-inch (6-mm) layer of raspberry buttercream on top of the chocolate layer. Continue alternating in that order-vanilla cake, raspberry preserves, ganache, chocolate cake, and raspberry buttercream- until you have topped the cake with the last chocolate layer. Spread an even layer of the remaining raspberry buttercream across the top.
Allow the buttercream top to set, uncovered, in the refrigerator for 30 minutes, and then cover the cake tightly with plastic wrap. Let the cake rest in the refrigerator for about 2 hours.
If the remaining ganache has hardened, place it over a bain marie until it is very loose. Spread a thin, even layer over the sides of the cake and transfer the remaining ganache to a large pastry bag fitted with a large star tip. Pipe the ganache in a filigree pattern along the perimeter of the top of the cake. Allow the cake to set at room temperature for about 20 minutes.