Mix crushed Oreos with melted butter until the crumbs look evenly coated, then press firmly into the bottom of a 9-inch springform pan. Freeze for 15 minutes until set and firm (watch for a solid, packed crust).

Spread the vanilla ice cream in an even layer over the Oreo crust, smoothing the top with the back of a spoon. Freeze for 1 hour until firm enough to hold its shape (it should look matte and not squish).

Drizzle the slightly cooled hot fudge sauce over the vanilla layer in a thin ribbon. Freeze for 15 minutes until the fudge is set (you should see it hold its streaks).

Spread the strawberry ice cream over the fudge layer and smooth the top, keeping the surface even. Cover with plastic wrap and freeze for at least 4 hours or overnight until fully firm (no soft spots when pressed lightly).

Run a warm knife around the edge, then release the springform and transfer the cake to a serving plate. Wipe the knife clean between passes for a sharp edge.

Pipe whipped cream swirls around the top edge, then scatter rainbow or patriotic sprinkles across the center. Slice with a hot knife, serve immediately, and keep slices clean for the best layered look.