Line a 9x13-inch baking pan with parchment paper. Set the ice cream on the counter to soften.
Place the Oreos in a gallon-size freezer bag and coarsely crush them with a mallet or rolling pin.
Transfer the crushed Oreos to a mixing bowl, reserving approximately ½ cup for the topping.
Add the melted butter and stir to combine.
Press the mixture evenly into the bottom of the prepared pan.
Spoon the softened ice cream over the crust and spread it into an even layer.
Freeze for 1–2 hours, until firm.
Warm the hot fudge sauce until pourable, then spread it over the ice cream layer. Freeze for 1 hour.
Spread the whipped cream over the hot fudge layer and sprinkle with the reserved crushed Oreos.
Freeze for at least 30 minutes or until ready to serve.
Let the cake sit at room temperature for a few minutes before slicing and serving.
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.