Line the sides of a 9 inch springform cake pan with plastic wrap (do not cover the bottom) by removing side panel from pan. I used several pieces to wrap around the sides. Secure plastic wrapped sides back onto the pan. Set aside.
Remove the chocolate ice cream from the freezer, and place contents into a large mixing bowl. Leave out for 15-30 minutes to soften, stirring every few minutes to promote even softening. Texture should resemble a velvety soft serve, in order to use in the recipe. Pour the softened chocolate ice cream to the prepared pan and spread into an even layer. Freeze for 45-60 minutes.
While chocolate ice cream layer is in the freezer, prep chocolate fudge and cookie layer.
In a double boiler, add all ingredients for fudge layer. Heat water to medium and slowly melt ingredients, while stirring very frequently. Once melted and well combined, remove from heat and set aside.
In a small food processor, add chocolate and vanilla cream cookies. Pulse a few times until cookies are well broken up. Set aside.
Remove the pan from the freezer, and pour the slightly cooled fudge over the chocolate ice cream and spread into an even layer. Working quickly, top the fudge layer with cookie crumbles (the cold layer will cause the fudge to freeze up very fast) and lightly press them into the fudge layer with hand palm or spatula. Return to freezer for another 30-45 minutes.
Remove the vanilla ice cream from the freezer, and place contents into a large mixing bowl. Leave out for 15-30 minutes to soften, stirring every few minutes to promote even softening. Texture should resemble a velvety soft serve, in order to use in the recipe.
Remove the cake pan from the freezer. Carefully pour the softened vanilla ice cream into the prepared pan and spread over the cookie/fudge layer, into an even layer. Freeze for 1-2 hours.
About 10 minutes prior to removing the cake from the freezer, prep the whipped icing layer and whipped pipping icing. For whipped icing layer (this will be applied all over the cake), combine the whipped cream and icing sugar. Stir well and refrigerate until you're ready to use. For whipped pipping icing (this is used for decor around the top and bottom of the cake), combine the whipped cream and cornstarch. Stir well and refrigerate until ready to use.
Remove the cake from the freezer and carefully detach springform pan sides. Using whipped icing layer, frost cake. If you intend on adding sprinkles or other candy decor to the cake, do so in this step. Return to freezer for 15-20 minutes and allow whipped icing layer to set.
Transfer whipped pipped icing to a pastry bag with your desired decorating tip. Remove cake from freezer and working quickly, pipe icing around top and bottom of the cake. Transfer to freezer for a minimum of 2 hours before serving.
Store uneaten cake in an airtight container in the freezer for up to a week.