Line bottom of 9-inch round cake pan with parchment or wax paper. Press cookie dough in bottom to 1/2 inch thickness. Bake approximately 18 minutes or until lightly brown. Cool completely.
In a large bowl, put 1 1/2 cups chocolate chips and 5 cups whipping cream. Microwave on HIGH for 4 – 5 minutes until chocolate is soft. Remove and stir well until chocolate and cream are mixed well. Cover with plastic wrap and chill overnight.
Melt remaining chocolate chips with butter and stir until smooth.
Place large cookie in center of 10-inch springform pan. Cut candy bars long ways and dip on end in chocolate mixture. Place vertically between cookie and sides of pan. Continue until all candy bar pieces are used.
Chill 20 minutes.
Whip cream and chocolate mixture until stiff.
Chop remaining candy bars into chunks. Take cookie shell and place one-third of mousse on bottom. Sprinkle chunks on top. Repeat layers, ending with mousse. Chill in freezer overnight.
Top with whipped cream and chunks of candy bar.
Return to freezer.
When ready to serve, remove from freezer and let stand in refrigerator 30 minutes before slicing.