1. Place the chopped chocolate candy bars in a small bowl; set aside.
2. Microwave 1/2 cup whipping cream for 1-1/2 minutes on HIGH then pour the hot cream over the chopped chocolate, let stand 5 minutes, then stir until smooth.
3. Using an electric mixer beat cream cheese, brown sugar and vanilla in a medium bowl until smooth.
4. Add remaining 1/4 cup of cream then gently beat in chocolate mixture.
5. Fold in 1/2 cup chocolate covered toffee bits.
6. Pour the filling into prepared chocolate crust.
7. Spread the 2 cups Cool Whip thawed topping over filling then top with remaining toffee bits.
8. Refrigerate for 2 or more hours before serving.