For the Crust:
20 Oreo cookies, crushed into crumbs
4 tablespoons unsalted butter, melted
2 to 3 bananas, sliced ½-inch thick
For the Whipped Cream:
1 cup heavy cream
2 tablespoons granulated sugar
1 teaspoon vanilla extract
1. Spray an 8x3-inch springform pan with nonstick cooking spray. Line the bottom and sides with parchment paper; set aside.
2. Assemble the Crust: Combine the Oreo cookie crumbs with the melted butter, tossing until all of the crumbs are evenly moistened. Press into an even layer in the bottom of the prepared pan. Top with the banana slices. Place the pan in the freezer for at least 15 minutes.
3. Assemble the Strawberry Layer: Top the banana layer with the strawberry ice cream. Use an offset spatula to spread the ice cream into a smooth, even layer. Place the pan back in the freezer for at least 30 minutes.
4. Pour the strawberry topping over the strawberry ice cream and gently spread so that it covers the entire ice cream layer beneath. Return to the freezer for at least 1 hour, or until completely frozen.
5. Assemble the Chocolate Layer: Top the strawberry layer with the chocolate ice cream. Use an offset spatula to spread the ice cream into a smooth, even layer. Place the pan back in the freezer for at least 30 minutes, or until firm and set.
6. Pour the hot fudge sauce over the chocolate ice cream and gently spread so that it covers the entire ice cream layer beneath. Return to the freezer for at least 1 hour, or until completely frozen.
7. Assemble the Vanilla Layer: Top the hot fudge layer with the vanilla ice cream. Use an offset spatula to spread the ice cream into a smooth, even layer. Cover with plastic wrap, return the assembled cake to the freezer and freeze overnight.
8. Final Assembly and Garnishment: At least 1 hour (and no more than 12 hours) before serving, unmold the cake. To release the cake from the pan, invert the cake onto a plate or cardboard round the same size and wrap a hot kitchen towel around the cake pan, keeping it there for 30 seconds, or until the cake loosens and slide the pan off. Remove the parchment (and bottom of pan if using a springform). Top with a serving plate and turn the cake right side up. Return to the freezer for at least 10 minutes.
9. While the cake is in the freezer, make the whipped cream. Combine the heavy cream, sugar and vanilla extract in the bowl of a stand mixer. Using the whisk attachment, whip on medium-high speed until the cream is light and fluffy and holds a medium to firm peak, 2 to 3 minutes.
10. Just prior to serving, pipe the whipped cream into mounds around the outer edge of the cake. Top each mound with a maraschino cherry. Fill in the space in the middle with the pineapple topping and top with chopped walnuts. A hot, dry knife will yield the cleanest cuts. Dip your knife in a glass of hot water, wipe it clean with a towel, and cut a slice. Repeat between every slice. Store leftover slices in airtight containers (or covered with plastic wrap and foil) in the freezer.
Note: If you are making homemade ice cream, your best bet is to time the assembly so that you can add the freshly-churned ice cream right onto the cake. It will be the perfect consistency. If you will be using already-made ice cream, pop it in the refrigerator for about 30 minutes before you plan to need it and then mix it really well with a spatula so that it is smooth and spreadable.