For the chocolate glaze:
1/4 cup heavy or whipping cream
1/4 cup light corn syrup
4 oz. semisweet chocolate, chopped
1 Tbs. unsalted butter
1 Tbs. whiskey or liqueur (optional)
For the cake:
1 oz. (2 Tbs.) unsalted butter
8 oz. good-quality bittersweet or semisweet chocolate, chopped
1/4 cup strong coffee or whiskey, or a mix
7 large eggs
1 cup granulated sugar
1/4 tsp. table salt
Confectioners’ sugar for dusting
For the mascarpone-cream filling:
1 cup mascarpone cheese
1-1/4 cups heavy or whipping cream
3 Tbs. granulated sugar
1 tsp. pure vanilla extract
For the final assembly:
1-1/2 cups fresh raspberries
Confectioner's sugar for dusting
Make the glaze:
In a small saucepan, mix the cream with the corn syrup. Stir over medium heat until the syrup dissolves, and then bring the mixture to a full boil. Remove from the heat, and add the chocolate all at once. Let stand for 2 minutes and then whisk until smooth. Whisk in the butter and then the whiskey or liqueur, if using. Keep at room temperature if using the same day; otherwise, cover and refrigerate.
Make the cake:
Heat the oven (not a convection oven) to 375°F. Grease a jellyroll pan or half sheet pan (about 11x16 inches) and line the bottom and long sides with parchment. Grease the parchment or spray it with baking spray.
In a small heavy-based saucepan (or a double boiler), melt the butter, chocolate, and coffee or whiskey over very low heat, stirring with a whisk occasionally. Take care not to let the chocolate scorch and heat only until the chocolate has melted. Remove from the heat, whisk until the mixture is smooth and glossy, and set aside to cool slightly while you beat the eggs.
Separate the egg yolks and whites into two large clean mixing bowls. Using an electric mixer (either a hand or a stand mixer) on medium high, beat the egg whites first until soft peaks form. Add about 2 Tbs. of the sugar and beat on high speed for about 30 seconds. Set aside.
Without cleaning the beaters or whip, beat the egg yolks on medium high, with the salt and the remaining sugar, until the mixture becomes light and thick and forms a ribbon trail when the beaters are lifted, about 3 minutes with a hand mixer, slightly less with a stand mixer. Turn the mixer to low speed, add the chocolate, and mix until completely blended, scraping down the sides of the bowl with a rubber spatula as needed.
With a clean whisk, vigorously beat the whites until a definite peak forms, about another 30 seconds.
Transfer about one-third of the whites into the bowl with the chocolate and fold them in with a rubber spatula. The whites should be smooth and blend into the chocolate thoroughly. Now scrape all of the chocolate mixture at once into the bowl with the remaining whites. Fold together lightly to blend, but don’t overwork—try to preserve as much volume as possible. Scrape the batter into the prepared pan and smooth the top with the spatula. Give the pan a gentle rap on the table to release any large air bubbles.
Put the pan in the middle of the heated oven and bake for 15 minutes. Turn the oven down to 325°F and let the cake cook another 5 minutes. The cake should look puffed, and a toothpick should come out clean.
Transfer the pan to a cooling rack. Moisten a clean, flat-weave (not terry-cloth) dishtowel and wring it out completely so it’s just barely damp. Cover the cake with the towel; the cake will sink slightly as it cools. Once the cake has cooled, slide the pan into the fridge until chilled, about 1 to 2 hours. This will help the trimming and assembly process.
Make the filling:
In a medium bowl, beat the mascarpone, cream, sugar, and vanilla with an electric mixer on low speed until blended. Increase the speed to medium high and beat until the cream is thick and firm peaks form (don't overbeat or the mixture will curdle). Keep refrigerated until ready to assemble.
Assemble the cake:
Lift the towel off the cake. Carefully loosen the parchment from the pan and run a knife along the edges to free the cake from the parchment. Dust the top of the cake generously with confectioners’ sugar. Lay a large piece of parchment, a large cutting board, or a dry dishcloth perfectly flat over the cake, pulling taut on both ends, and with a deep breath, invert the cake onto a work surface, long side facing you. Gently peel away the parchment.
With a large, sharp knife, carefully trim about 1/4 inch off the edges to get an even rectangle. Use a slow sawing motion to avoid tearing the cake; a light coating of confectioners’ sugar on the knife will prevent sticking. Cut the rectangle crosswise into four even panels, each about 4x10 inches. Slide a long spatula or a long, wide knife, like a bread knife, under the first panel and carefully transfer it to a flat serving platter.
Tuck strips of parchment, plastic wrap, or foil under the edges of the cake layer and over the plate to keep the plate clean during assembly. Spread one-third of the filling evenly over the cake layer. Sprinkle one-third of the raspberries over the cream and press them in gently. Top with a second cake panel and another third of the cream and berries. Top with a third cake panel and the remaining cream and berries. Arrange the final cake layer on top and press gently.
Dust the top of the cake generously with more confectioners’ sugar. Drizzle the chocolate glaze over the top of the cake. Carefully slide the parchment strips away from the plate. Refrigerate the cake until about 15 minutes before serving.
Make Ahead Tips:
The glaze can be made up to four days ahead and refrigerated. Let it come to room temperature before using. The cake can be made up to one day ahead. Refrigerate it with a sheet of plastic stretched taut across the top of the pan so it doesn't touch the cake surface. The filling can be made up to an hour before assembly. The whole cake can be assembled the morning of the day you want to serve it, but don't decorate the top with confectioners' sugar and glaze until two hours before serving. Keep the fully decorated cake in the fridge, uncovered, until about fifteen minutes before serving.
