Preheat oven to 350 degrees F. Place the crushed pretzels, sugar, and melted butter in a bowl. Stir until combined. Press the pretzel mixture into the bottom and up the sides of a 9-inch pie pan. Bake for 8-10 minutes. Remove from oven and let cool completely.
In a large bowl, stir together the ice cream and peanut butter. Pour the ice cream mixture into the cooled pretzel pie crust. Smooth with a spatula and top with the chopped up peanut butter cups. Place pie in freezer and freeze until ice cream hardens, at least 2 hours.
When ready to serve, remove pie from freezer. Drizzle pie with Peanut Butter Hot Fudge Sauce. Run a sharp knife under hot water. Cut the pie into slices and serve immediately.
Note-to make the pretzel pie crust, you will need about 4 cups whole pretzels. To crush them, you can place the pretzels in a zipped plastic bag and crush with a rolling pin. Alternately, you can use a food processor. The pie will keep in the freezer for up to 2 weeks. Keep the pie covered with plastic wrap. You can find Private Selection ice cream at Kroger stores.