Adding chocolate mousse, frosting and ganache to doughnuts may seem like gilding the lily, but so what? Pass it off as the last dessert of the year and start your resolutions on New Year's Day. Serve the bombe with lightly sweetened whipped cream and fresh berries on the side. To serve, cut it in the style of a wedding cake, by making a circle incision halfway between the perimeter and the middle before slicing.
Day 1 (takes 1 to 11/2 hours): Line the bowl with doughnuts, make the chocolate mousse and fill the bowl with the mousse, cover with doughnuts and freeze.
Day 2 (1 hour): Frost the bombe and glaze with ganache.
*Note: You may substitute any chocolate frosting or buttercream. This is the basic Hershey chocolate recipe. Its purpose is to make a smooth surface on the bombe for the ganache.
Make Ahead: The bombe must be started at least 2 days in advance. It is made in 2 stages on 2 consecutive days. (It can be made up to 8 days ahead.)
- For the doughnuts
- 2 dozen fresh Krispy Kreme doughnuts, 18 cut in half horizontally, 6 whole doughnuts reserved for garnish
- For the chocolate mousse
- 1 1/2 pounds chopped semisweet or bittersweet chocolate
- 9 tablespoons cold coffee
- 6 large egg yolks
- 6 tablespoons confectioners' sugar
- 3 cups heavy cream, whipped
- 6 large egg whites, beaten stiff, not dry
- For the chocolate frosting
- 3/4 stick (3 ounces) unsalted butter, softened
- 2 2/3 cups confectioners' sugar
- 1/2 cup Dutch-process cocoa powder
- 1/3 cup whole milk
- 1 teaspoon vanilla extract
- For the chocolate ganache
- 4 cups heavy cream
- 2 pounds semisweet or bittersweet chocolate, coarsely chopped
Using a large stainless steel mixing bowl (20-cup, 13 inches in diameter), make a cake circle from the side of a cardboard box and cover it with aluminum foil. (Draw a circle on the cardboard around the circumference of the inverted bowl and cut out the circle.) Set the cake circle aside.
Line the bowl with a 40-by-23-inch sheet of plastic wrap (overlap two 40-by-12-inch sheets by 1 inch); this way the wrap will be long enough to cover the bowl once it is full. Line the inside of the bowl with the doughnut halves, cut sides facing inward. Start with a doughnut round on the bottom of the bowl and work your way outward, pushing the doughnuts together tightly. Fill any holes or open spaces with pieces of doughnut.
For the chocolate mousse: In a large mixing bowl set over a pot of hot water (to form a kind of double boiler), combine the chocolate and coffee, whisking until smooth and just blended. Transfer the bowl to a work surface and whisk in the egg yolks until smooth. Add the sugar, whisking to combine. (At this point, the mixture should be cool to the touch.) Fold in the whipped cream, and then the egg whites.
Pour the mousse into the doughnut-lined bowl stopping 1 inch short of where the doughnuts end. Cover the mousse with more doughnuts, making them level with the doughnuts lining the side of the bowl. Fill any spaces on the top with pieces of doughnut. Place the cake circle on the top. Cover the bowl with plastic wrap and freeze the cake overnight so it is frozen solid. Finish the cake at any time on the next day.
When ready to assemble, prepare the frosting. Using a stand mixer fitted with a whisk attachment on medium speed, cream the butter, sugar and cocoa. Reduce speed to low and with the mixer running, add the milk gradually. Increase the mixer speed and beat to a fluffy, spreadable consistency, adding more milk if necessary. Add the vanilla extract.
Remove the bombe from the freezer. Unwrap it and invert the bombe on a work surface. (The cake circle will now be on the bottom.) Remove the bowl and the plastic wrap. If there are any open spaces between the cake circle and the doughnuts, fill them in with doughnut pieces to make the surface of the bombe an even dome.
Use a metal cake spatula to spread the chocolate frosting on the bombe as smoothly as possible. Place the bombe on a wire rack placed over a rimmed baking sheet and refrigerate it while preparing the ganache.
For the chocolate ganache: In a large saucepan, bring the cream to a boil, then remove from the heat and add the chocolate. Whisk until the chocolate is smooth and completely melted. Transfer the ganache to a medium bowl and allow it to cool completely and thicken slightly, about 30 minutes. Remove the bombe, rack and pan from the refrigerator and pour enough ganache slowly from its bowl over the top of the bombe to coat the dome completely and smoothly. Apply 3 or 4 coats, stopping for a minute between coatings to let the ganache set.
(Ganache tips: Don't worry about wasting; any extra ganache will fall onto the baking sheet and can be saved for reuse. Don't touch the applied ganache with a utensil. Pour steadily for each coat and let the ganache do the work; when one coat is complete, let it set for about a minute before applying the next coat. Apply as many coats as you wish; the more you apply, the smoother the finish. A bumpy surface is not a tragedy; it will just make the cake look more charming than professional.)
Place the bombe in the refrigerator uncovered until the ganache is set completely, about 30 minutes. (At this point, it may be covered with plastic wrap without sticking.) The bombe can be returned to the freezer for up to a week. Otherwise, refrigerate until ready to serve.
Remove the bombe from the refrigerator 15 minutes before serving. If it's frozen, remove it 1 hour before serving. As a garnish for New Year's Eve, fashion the reserved doughnuts into the numbers signifying the new year and press them into the side of the cake. Light the cake with sparklers, if desired, and serve.
Adapted from chef and former restaurateur David Hagedorn.
Tested by Tom Wilkinson.
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