Make the crust: Crush the vanilla cookies into fine crumbs. Mix with melted butter and rainbow sprinkles. Press firmly into a 9-inch pie plate. Freeze while preparing the filling.
Prepare the cookie dough: Beat the softened butter, brown sugar, and granulated sugar until creamy. Mix in the milk and vanilla. Add the cooled, heat-treated flour and stir until a soft dough forms. Fold in the mini chocolate chips and sprinkles.
Make the filling: Stir the softened vanilla ice cream until smooth. In a separate bowl, whip the heavy cream with powdered sugar until soft peaks form. Fold the whipped cream and vanilla into the ice cream.
Add the sprinkles and cookie dough: Gently fold the rainbow sprinkles and most of the cookie dough pieces into the ice cream mixture. Reserve some cookie dough for decorating.
Fill the crust: Spoon the mixture into the chilled crust and smooth the top with a spatula
Decorate: Add the reserved cookie dough pieces, whipped cream, rainbow sprinkles, and mini chocolate chips.
Freeze: Cover tightly and freeze for at least 4 to 6 hours, preferably overnight.
Serve: Let the pie sit at room temperature for 5 to 10 minutes before slicing. For cleaner cuts, warm a sharp knife under hot water, dry it, and then slice.
