Line a 9X13 baking pan with parchment paper. Set aside.
Set the ½ gallon of ice cream on the counter to soften.
Place 1 package Oreos (13 ounces) in a gallon-size freezer bag and crush them coarsely with a mallet or rolling pin.
Place the crushed Oreos in a mixing bowl and reserve approximately ½ cup of the crushed Oreos for the topping.
Add 4 tablespoons melted butter to the bowl and stir to combine.
Press this mixture into the bottom of the prepared 9X13 baking dish.
Carefully spoon ½ gallon cookies and cream ice cream over the Oreo crust and spread it evenly into the pan with a spatula.
Place the baking dish into the freezer for 1-2 hours until firm.
Warm 1 jar hot fudge sauce (approximately 12 ounces) until it is easily pourable, then pour it over the ice cream layer. Place the pan back in the freezer for 1 hour.
Remove the pan from the freezer, spread 8 ounces whipped cream on top, and sprinkle the reserved ½ cup crushed Oreos over the whipped cream.
Freeze for at least 30 minutes or until ready to serve.
When ready to serve, let the cake sit at room temperature for a few minutes to soften some and then it’s ready to slice, serve and enjoy!
Notes
Store any leftover cake, covered, in the freezer for up to 1 month. Make sure to freeze each layer of the cake to ensure that they are able to layer on top of each other.