Preheat the oven to 375 degrees F. Spray the springform pan with cooking spray, line with a circle of parchment, and spray the parchment. Place the chocolate wafer cookies in the bowl of a food processor. Pulse until it makes fine crumbs. Add the melted butter and pulse to combine. Press the mixture into the bottom and halfway up the sides of the prepared springform pan. Bake until toasted and crisp, 15 minutes. Cool completely. Scoop alternating scoops of half of the ice cream and half of the sorbet into the crust using an ice-cream scoop. Smooth the top, filling in any gaps. Tile slices of pound cake over the ice cream. Cover with plastic wrap and freeze until firm, 30 minutes. Remove the cake from the freezer. Spread the hot fudge sauce over the cake slices. Scoop the remaining ice cream and sorbet onto the hot fudge sauce and smooth the top. Cover with plastic wrap and freeze until completely set, 4 hours.
Immediately prior to serving, make the whipped topping. Whip the cream into semi-soft peaks, and then add the powdered sugar and vanilla and continue to whip to stiff peaks. To serve, remove the plastic wrap and coat the top of the cake with the whipped topping using an offset spatula while still in the springform pan. Release the cake from the sides of the pan with a knife and remove the ring. Garnish with cocoa powder and raspberries and serve.
Easy variations for ice cream cake - cookie crust can be made using shortbread cookies, vanilla cookies, etc. The cake can easily be frosted with a ganache to just cover the top of the cake - just make sure that your cake is well frozen prior to topping with a warm ganache. Fruit jams could be used as a filling in place of hot fudge. Other things that hold up as well as pound cake - brownies, chocolate chip cookies, ice cream sandwiches.