Prep your pan. Line a 9-inch springform pan or a loaf pan with plastic wrap or parchment, leaving overhang for easy lifting.
Chill the pan in the freezer for 15 minutes so the first layer sets quickly.
Soften the ice cream. Place your first ice cream flavor on the counter for 10–15 minutes, until scoopable and spreadable but not melted. Stir it a few times to even out the texture.
Make the crunchy base. Pulse cookies or crackers into fine crumbs. Mix with melted butter and a small pinch of salt until it looks like damp sand.
Press firmly into the bottom of the cold pan to form a compact crust. Freeze for 10 minutes.
Add the first ice cream layer. Spoon softened ice cream over the crust. Spread into an even layer with an offset spatula or the back of a spoon.
Freeze for 20–30 minutes, until slightly firm.
Drizzle sauces. Spread a thin, even layer of warm hot fudge over the ice cream. If using caramel, add it now in a light swirl. Keep layers thin so the cake slices cleanly.
Freeze for another 10 minutes.
Add more crunch. Sprinkle a light layer of dry crumbs or mini chips over the sauce. This adds texture and keeps layers from slipping. Freeze again for 10 minutes.
Add the second ice cream layer. Soften your second flavor as before.
Spread gently over the crumb layer. Aim for smooth, level edges to make unmolding easier. Freeze for 30–45 minutes.
Finish with whipped cream. Spread or pipe whipped cream over the top.
Keep the layer modest so it firms up well. Return to the freezer for at least 2 hours, or until fully solid.
Garnish and set. Just before the final freeze, add sprinkles, nuts, or extra crumbs. Press them lightly so they stick.
Freeze at least 4 hours total, or overnight, for the cleanest slices.
Unmold and slice. Run a warm, thin knife around the edge of a springform pan, or lift using the parchment overhang if using a loaf pan. Warm your knife under hot water, wipe it dry, and slice in quick, confident strokes. Return slices you’re not serving to the freezer right away.