Prep the pan: Line a 9-inch springform pan with parchment on the bottom. If you don’t have one, use a loaf pan lined with plastic wrap, leaving overhang to lift the cake out later.

Soften the ice cream: Set both flavors on the counter for 10–15 minutes until scoopable. You want it soft enough to spread but not melted.

Make the cookie crust: Crush the chocolate sandwich cookies in a food processor or sealable bag until fine. Stir in melted butter and a pinch of salt. Press firmly into the bottom of the pan to form an even layer. Freeze for 10 minutes.

First ice cream layer: Spread the first flavor over the crust, smoothing to the edges. Tip: Use an offset spatula warmed under hot water and dried to help spread cleanly.

Fudge layer: Warm the fudge sauce just until pourable—about 10 seconds in the microwave. Drizzle and gently spread over the ice cream. Don’t press hard or it will blend.

Chill briefly: Freeze for 15–20 minutes so the fudge firms and layers stay distinct.

Second ice cream layer: Add the second flavor on top, smoothing evenly. If you like, sprinkle a handful of crushed cookies or mini chips between scoops to add texture.

Freeze to set: Cover tightly and freeze at least 4–6 hours, preferably overnight, until very firm.

Whip the topping: If using heavy cream, whip with powdered sugar and vanilla to medium peaks. If using whipped topping, keep it chilled until ready to use.

Unmold and frost: Run a warm knife around the pan edge, then release the springform. Frost the top and sides with whipped cream or topping. Work quickly so the cake doesn’t soften too much.

Decorate: Add sprinkles, more crushed cookies, or a drizzle of fudge. For clean edges, freeze again for 30 minutes before slicing.

Serve: Use a sharp knife run under hot water and dried between cuts for neat slices.