Prepare the DishLightly grease an 8×8-inch or 9×9-inch baking dish with non-stick spray. Set aside.
Make the CrustPlace shortbread cookies in a Ziplock bag and crush into fine crumbs using a rolling pin. Transfer to the baking dish, mix with melted butter, and press evenly to form the crust. Freeze for 20 minutes.
Build the FillingIn a mixing bowl, combine softened vanilla ice cream with half of the chopped Twix bars. Spread the mixture evenly over the chilled crust.
Add Toppings and FreezeSprinkle the remaining Twix pieces on top. Cover and freeze the cake for at least 6 hours or overnight for best texture.
Finish with DrizzleMelt chocolate chips in the microwave in 20-second intervals, stirring between bursts until smooth. Drizzle melted chocolate and caramel topping over the frozen cake.
Slice and ServeCut into squares and serve immediately. Keep any leftovers frozen in an airtight container for up to 3 months.