Spray a 9x13 pan with cooking spray. In medium bowl, melt 1/2 cup of butter in the microwave for about 30 seconds. Add graham cracker crumbs to butter, and 3/4 cup of heath bits, mix well. Press mixture into the pan and refrigerate while you do the next step.
Get cookie dough out of the refrigerator so it can soften a little. Preheat oven to 350. In a medium saucepan, add chocolate chips, sweetened condensed milk, and 1 tablespoon of butter. Cook over medium heat until chocolate is melted and smooth. Remove from heat, stir in vanilla. Spread mixture over crust.
Break apart cookie dough and crumble over chocolate or flatten pieces in your hand and place over chocolate. Try to cover the whole top of dish. There will be holes but when it bakes it will spread out. Sprinkle with remaining 3/4 cup of heath bits.
Bake for 20 to 25 minutes or until golden brown. Cool.