Bake the 8-inch cake layer ahead of time according to mix directions. Wrap and freeze individually. You'll only use one layer.
Soften the ice cream on the counter, about 15 minutes. Meanwhile, line your 8-inch cake pan with parchment paper. When ice cream is soft, press it into cake pan and freeze; overnight works best.**
Mix the filling by combining 1/2 cup room temperature hot fudge sauce with the crushed Oreos.
Place one prepared and frozen 8-inch cake round on a platter or cake stand that can go in the freezer.
Spread the filling over the top of the cake layer.
Top the filling with the prepared round of ice cream.
“Ice” the cake with the entire thawed Cool Whip container. Decorate the top of the cake with 1 tablespoon room temperature hot fudge sauce pushed through a tiny hole in a zip closure bag (twist bag to force the sauce toward the hole and squeeze the bag consistently to get that thin drizzled effect).
*For variations, substitute other cake mix and ice cream flavors.
**If your cake pans are 9 inches, use them for the cake and ice cream layers. Adjust filling to 3/4 cup room temperature hot fudge sauce and about 13 crushed Oreos.
My cake layer shrunk during baking so the ice cream layer was too wide. I used a hot knife (dipped in hot water and dried) to carve the ice cream round to fit the cake layer. Use the shaved ice cream to fill in any spaces between the cake layer and the ice cream layer before "frosting".
If ice cream becomes soft while frosting, return to the freezer for 15 minutes then proceed.
After adhering the Oreo rounds to the side of the cake, I returned the cake to the freezer for 15 minutes to firm up the "frosting" before adding the chocolate drizzle.
I used a gluten-free, dairy-free cake, gluten-free Oreos, vegan chocolate sauce, vegan ice cream, and vegan whipped topping, which is softer than Cool Whip. I found it necessary to apply a light layer of the topping over the cake, freeze for 15 minutes, then apply another layer of the topping.
https://cinnamonsugarandalittlebitofmurder.com