Preheat the oven to 350 degrees F. In a medium bowl, combine shortbread cookie crumbs and melted butter. Press into an ungreased 9-inch pie dish. Bake for 10 minutes. Let crust cool on a wire cooling rack.
In a microwave safe bowl, melt the chocolate chips, stirring occasionally. Pour melted chocolate in the bottom of the pie crust. Put the crust in the freezer until the chocolate hardens, about 15-20 minutes.
While the chocolate is hardening, remove your ice cream from the freezer to soften. Once softened, stir in the salted caramel sauce and 1 cup of the chopped Twix candy bars.
Remove crust from freezer and pour ice cream mixture into the crust. Smooth the top. Garnish with the remaining 1 cup chopped Twix candy bars and salted caramel sauce. Carefully cover pie with plastic wrap, making sure it doesn't touch the pie. Place pie in freezer and freeze until ice cream hardens, at least 2 hours.
When ready to serve, remove pie from freezer. Run a sharp knife under hot water. Cut the pie into slices and serve immediately.
Note-to make the cookie crumbs for the crust, place the cookies in a zipped plastic bag and crush with a rolling pin. Alternately, you can use a food processor.