Step 1: Prepare the Pan
Line the bottom of a 9-inch springform pan with parchment paper for easy removal. Lightly spray the sides with cooking spray or brush with a thin layer of melted butter to prevent sticking.

Step 2: Make the Cookie Crust
Place chocolate sandwich cookies (including the cream filling) in a food processor and pulse until fine crumbs form, about 30-45 seconds. Alternatively, place cookies in a large zip-top bag and crush with a rolling pin until finely ground. Transfer crumbs to a large bowl, add melted butter, and stir with a fork until mixture resembles wet sand and holds together when pressed. All crumbs should be evenly moistened.

Step 3: Press the Crust
Pour cookie crumb mixture into the prepared springform pan. Using the bottom of a measuring cup or your fingers, press crumbs firmly and evenly across the bottom of the pan, creating a compact layer that extends slightly up the sides (about ½ inch). Place pan in freezer while preparing the first ice cream layer, at least 15 minutes.

Step 4: Add First Ice Cream Layer
Remove ice cream from freezer and let sit at room temperature for 5-10 minutes until slightly softened and spreadable (it should have the consistency of thick frosting, not melted). Remove springform pan from freezer. Scoop first ice cream flavor over the cookie crust. Using a rubber spatula or offset spatula, spread ice cream evenly across the crust, smoothing the top as much as possible. Work relatively quickly to prevent excessive melting. Return pan to freezer and freeze until firm, at least 1 hour or up to overnight.

Step 5: Add Fudge Layer
Warm hot fudge sauce according to package directions until pourable but not hot (you want it fluid but not so hot it melts the ice cream). Remove cake from freezer. Pour fudge sauce over the first ice cream layer, using a spatula to spread it evenly to the edges. Return to freezer for 30 minutes to set the fudge layer.

Step 6: Add Second Ice Cream Layer
Soften the second ice cream flavor the same way you did the first. Remove cake from freezer. Scoop second ice cream flavor over the fudge layer. Spread evenly and smooth the top with a spatula, creating a flat surface for the whipped cream topping. Cover pan completely with plastic wrap or aluminum foil, pressing directly onto the surface to prevent ice crystals. Freeze until very firm, at least 4 hours or preferably overnight.

Step 7: Make Whipped Cream Topping
When ready to serve (or up to 4 hours before), make the whipped cream topping. Place a large mixing bowl and beaters in the freezer for 10 minutes to chill. Pour cold heavy cream into the chilled bowl. Beat on medium speed until cream begins to thicken, about 1-2 minutes. Add powdered sugar and vanilla extract. Increase speed to medium-high and continue beating until stiff peaks form, about 2-3 minutes total. Be careful not to overbeat, or cream will become grainy.

Step 8: Frost and Decorate
Remove cake from freezer and remove plastic wrap. Run a thin knife around the inside edge of the springform pan to loosen any stuck areas. Carefully release and remove the springform ring. Transfer cake (still on the springform base) to a serving plate. Spread whipped cream evenly over the top of the cake, creating swirls or a smooth finish as desired. You can also pipe the whipped cream using a piping bag for a more decorative look. Add your chosen toppings immediately – sprinkles, chocolate chips, crushed cookies, drizzled chocolate sauce, or whatever complements your ice cream flavors.

Step 9: Final Freeze and Serve
If not serving immediately, return decorated cake to freezer for at least 30 minutes to set the whipped cream. The fully assembled cake can be frozen for up to 5 days, covered loosely with plastic wrap once the whipped cream is frozen solid. When ready to serve, remove cake from freezer and let sit at room temperature for 5-10 minutes to make slicing easier. Dip a sharp knife in hot water, wipe dry, and slice into wedges, cleaning the knife between cuts for neat slices.