Allow the ice cream to sit out long enough to soften, but don't let it melt! Warm the hot fudge topping slightly in a saucepan over low heat for ease of spreading and spread about half of it into the bottom of the crumb crust. Mash the ice cream carefully over the hot fudge topping, spreading it evenly over the pie. Place the pie in the freezer for a few hours. Also, place the peanut butter cups in the freezer.
Remove the pie from the freezer. Warm the remaining hot fudge topping, but not so much that it will melt the ice cream. Spread the topping over the ice cream. To serve, space eight dollops of whipped cream around the pie. Place the pie back into the freezer and let the pie set for about 25 minutes before serving. Cut the frozen peanut butter cups into quarters and place each quarter on each dollop. Slice into eight pieces.