Place cookies in a gallon size zip-top bag. Using a rolling pin, crush Oreos into medium sized chunks (not fine crumbs). Reserve 1 cup for topping and set aside. Add melted butter to the remaining crushed Oreos and flatten onto the bottom of a 9x13-inch baking dish.
Spread soft ice cream into an even layer over the crushed cookie crust. I cut out rectangle pieces with a knife, and smoothed them together. Freeze until set; time will depend on how soft the ice cream is.
Remove lid and warm fudge in the microwave until a spreadable consistency; about 45-55 seconds. Drizzle over the ice cream and spread evenly with a spatula. Freeze until set; about 30 minutes.
Top with whipped topping and crushed Oreos. Freeze for 2 hours or until firm. Remove from freezer 10 minutes before serving. Dip knife into hot water to make slicing easier. Wipe blade clean periodically with a paper towel. Enjoy!