Note: I made this cake for my husbands birthday this weekend and it was a disaster! I attempted to create a roll cake using a box cake mix and it stuck to the towel as I unrolled it. I did the best I could with it...rolling it up in saran wrap & securing it with packing tape (I wish I had taken a photo!). The end result tasted great, and each slice looked acceptable, but the cake as a whole was not pretty. So, for your sake, I am modifying the directions here to create an actual ice cream cake rather than a roll :)
6 cups, not packed, vanilla ice cream (I use Blue Bell No Sugar Added)
1 package mini peanut butter cups, divided
1 box cake mix (I used vanilla, but white, yellow or chocolate would work just as well)
Hot fudge (store bought or homemade)
Prepare cake mix as directed and bake in 2 rounds. Place 1/3 of the bag of peanut butter cups in the freezer for later use. Allow the cakes to cool completely, wrap each layer in saran wrap and freeze.
When ready to assemble, unwrap 3/4 of the peanut butter cups and set aside. Then, remove rounds & ice cream from freezer. Determine which layer will be the top and set it aside. Cut the rounded top off the other layer so the top is completely flat.
Place ice cream and peanut butter cups in a large bowl and mix with an electric mixer until well combined. Quickly spread a generous layer of the ice cream mixture on the bottom section of cake, then stack the additional layer of cake on top. Wrap the entire cake in saran wrap and refreeze.
Remove from freezer 10-15 minutes before serving. During this time, chop the frozen peanut butter cups and heat the fudge. Generously drizzly the fudge on the cake & sprinkle with the chopped peanut butter cups.