Line an 8x8 inch square pan with parchment paper, make sure the paper goes all the way up the sides.

Add the chocolate sandwich cookies to the bowl of a food processor and pulse until all the cookies are crumbs. Add the butter and pulse to combine.

Transfer the cookie crumbs to the prepared pan and press into the bottom and up the sides as evenly as possible. Freeze for 10 minutes.

When the ice cream is soft, carefully spread it evenly over the crust and smooth out the top.

Heat the hot fudge sauce (if cold) until it is thin enough to pour but not hot. Pour the hot fudge over the ice cream and smooth it out as evenly as possible. Freeze (flat!) for at least 2-4 hours before serving.

To serve, use the parchment paper to remove from the pan and slice into squares. Top with whipped cream if desired. Keep frozen until ready to serve.