Death By Chocolate: Assemble Death By Chocolate
Place a closed 9 by 3-inch spring-form pan on a baking sheet. Set the top half of the chocolate brownie inside the pan top side up. Ladle 1 1/2 cups of ganache into the pan over the chocolate brownie. Trim the cocoa meringue with a serrated knife so that it will fit tightly into the pan. Place the trimmed cocoa meringue, top side up, inside the pan on top of the ganache, pressing down gently on the cocoa meringue to eliminate air pockets.
Spoon the mocha mousse on top of the cocoa meringue spreading evenly. Place the remaining chocolate brownie half, bottom side up, on top of the mocha mousse. Chill the cake in freezer for 30 minutes or refrigerate for 1 hour.
Remove from the freezer and cut around the edges to release from the spring-form pan. Pour the remaining ganache over the cake and use a cake spatula to spread the ganache evenly over the and sides of the cake. Refrigerate the cake for 10 to 15 minutes to set the ganache.
Fill a pastry bag with a star tip with the chocolate mousse. Pipe a circle of stars (each touching the other) along the outside edge of the top of the cake. Continue to pipe out circle of stars until the top of the cake is covered. Refrigerate the Death By Chocolate for at least 4 hours and preferably 12 hours before cutting and serving.
Heat the butter in a 2 1/2 quart saucepan over medium heat. When melted, add the sugar, heavy cream, sifted cocoa, 2 tablespoons dark rum, and salt. Stir with a whisk to combine. Bring to a boil, then adjust heat and allow to simmer for 5 minutes, occasionally stirring. Remove the saucepan from the heat. Add the instant coffee and vanilla extract and remaining tablespoon of rum, stir until smooth. Allow to cool to room temperature before serving.
To serve, cut the Death By Chocolate into the desired number of servings. Heat the blade of a serrated slicer under hot running water before slicing into the cake. Repeat this procedure after making each slice. Flood the base of each 10-inch dinner plate with 3 to 4 tablespoons mocha rum sauce and place a piece of Death By Chocolate in the center of each plate. Serve immediately.