How to Make an Ice Cream Cake
Bake the Cake
Prepare the buttermilk devil's food cake batter in a stand mixer, then scrape into a greased 8-inch springform pan and bake. Let cool completely.
Slice Off the Top
Using a serrated knife, shave a 1/4-inch slice off the top of the cake to level the surface.
Break up the thin cake top and pulse in a food processor until fine crumbs form. Bake until crisp, then let cool completely.
Set Up the Mold
Wrap a sheet of acetate around the cake to form a support collar, then reattach and secure the ring.
Make hot fudge sauce and let cool, then spread half of it over the cake in an even layer. Top with a layer of chocolate crunchies and freeze the cake until firm.
Add Ice Cream
Spread chocolate chip ice cream on the cake in an even layer, followed by more chocolate crunchies, fudge, strawberry ice cream and whipped cream.
Bring heavy cream to a boil. Place chopped bittersweet chocolate in a heatproof bowl and pour the hot cream on top. Let stand until the chocolate is melted, then whisk until smooth.
Unmold the Cake
Remove the springform ring and transfer the cake to a plate or to a rack set over a baking sheet. Peel off the acetate.
Decorate and Serve
Pour the ganache onto the cake and freeze until set. Decorate with whipped cream stars and maraschino cherries and sprinkles if desired. Cut the cake with a hot knife, wiping off the knife between cuts.