for the cake
4 1/2 ounces high-quality bittersweet chocolate, finely chopped
9 tablespoons (1 stick plus 1 tablespoon) unsalted butter, room temperature
1 cup confectioners’ sugar
6 large eggs, separated, at room temperature
1 teaspoon vanilla extract
1/2 cup granulated sugar
1 cup all-purpose flour
for the glaze and decoration
1 cup seedless raspberry jam
2 tablespoons rum
1 1/2 cups sugar
3/4 cup water
6 ounces high-quality bittersweet chocolate, coarsely chopped
at least 2 boxes of Mikado stick snacks
additional decorations (i.e. flowers) as desired
Make the cake (can be made up to 2 days ahead): Preheat oven to 400F. Lightly butter a 9-inch spring form pan and line the bottom with a round of parchment or wax paper. Dust the sides of the pan with flour and tap out the excess.
In the top part of a double boiler over very hot, but not simmering, water, or in a microwave at medium power, melt the chocolate. Remove from the heat or the oven, and let stand, stirring often, until cool.
Beat the butter in the bowl of a stand mixer fitted with the paddle blade on medium-high speed until smooth, about 1 minute. On low speed, beat in the confectioners’ sugar. Return the speed to medium-high and beat until light in color and texture, about 2 minutes. Beat in the egg yolks, one at a time, scraping down the sides of the bowl. Beat in the chocolate and vanilla.
Beat the egg whites and granulated sugar in a large bowl with an electric mixer on high speed just until they form soft, shiny peaks. Do not overbeat. Stir about one fourth of the beaten whites into the chocolate mixture to lighten it, then fold in the remaining whites, leaving a few visible wisps of whites. Sift half of the flour over the chocolate mixture, and fold in with a rubber spatula. Repeat with the remaining flour.
Spread evenly in the pan. Bake until a toothpick inserted in the center comes out clean, about 45 minutes. (The cake will dome in the center.) Cool on a wire rack for 10 minutes. Remove the sides of the pan, and invert the cake onto the rack. Remove the paper and re-invert on another rack to turn right side up. Cool completely.
Heat raspberry jam and rum in a small saucepan and stir with a whisk until very smooth.
To Assemble: Using a long serrated knife, trim the top of the cake to make it level. Cut the cake horizontally into two equal layers. Place one cake layer on an 8-inch cardboard round. Brush the top of the cake layer with the raspberry glaze. Place the second cake layer on top and brush again. Brush the top and sides of the cake with the remaining glaze. Transfer the cake to a wire rack placed over a jelly-roll pan lined with waxed paper. Let cool until the glaze is set.
Make the chocolate glaze (it must be freshly made and warm): In a heavy-bottomed medium saucepan (no larger than 2 quarts, or the mixture will reduce too rapidly and burn before it reaches the correct temperature) over high heat, bring the sugar, water, and chocolate to a boil over medium-high heat, stirring occasionally. Attach a candy thermometer to the pan. Reduce the heat to medium and cook, uncovered, stirring, until the mixture reaches 235F, about 5 minutes.
Remove from the heat and stir to cool and thicken slightly, about 1 minute. Use immediately.
Pour all of the warm chocolate glaze on top of the cake. Using a metal offset spatula, gently smooth the glaze over the cake, allowing it to run down the sides, being sure that the glaze completely coats the cake (patch any bare spots with the spatula and the icing that has dripped). Cool until the glaze is barely set, then transfer the cake to a serving plate. Working as efficiently as possible (you might need a second set of hands to help you out here), rim the outside of the cake with the Mikado snacks to create the outside/fence of the “hot tub”. Tie with a ribbon (alternatively, you can also tie with baker’s twine and then tie the prettier ribbon around later). Add piggy decorations. Refrigerate for a few hours to let the chocolate set.
Remove the cake from the refrigerator about 30 minutes before serving. To serve, slice with a sharp knife dipped into hot water.