Place peanut butter cookies in a food processor and pulse until crumbs are formed. Mix butter with crumbs. Press crumbs into the bottom of a 9-inch springform pan to form a crust.
Heat hot fudge in the microwave for 30 seconds or until runny. Spread a thin layer of fudge over the crust. Place the pan in the freezer for one hour, or until fudge is set.
Allow ice cream to soften at room temperature. Put softened ice cream in the pan on top of the fudge and crust. Press to shape in pan and return to freezer for an hour. Remove from freezer and top with remaining fudge (may need to reheat in microwave) and chopped Reese's peanut butter cups. Cover and freeze until solid.