Spoon caramel ice cream evenly into chocolate crust; sprinkle with half of crushed toffee bars. Freeze 10 minutes.
Spoon chocolate chunk ice cream evenly over toffee layer. Freeze 10 minutes. Spread whipped topping evenly over chocolate ice cream layer. Drizzle with chocolate syrup, and sprinkle with remaining crushed toffee bars. Freeze at least 8 hours or overnight.