Preheat oven to 325 degrees F. Line a 13 x 9 inch baking pan with foil extending over the sides. Spray lightly with nonstick cooking spray. Set aside.

In a large bowl, combine Graham Cracker crumbs, melted butter and brown sugar. Stir until evenly combined then press mixture firmly and evenly into the bottom of the prepared pan. Bake for 12 minutes. Cool crust in pan on a wire rack for 5 minutes.

Meanwhile, microwave caramels and heavy cream together in a medium bowl until smooth, stirring every 30 seconds until melted, about 2 minutes. Pour caramel mixture over crust and spread evenly.

Sprinkle caramel with marshmallows, nuts and chocolate, slightly pressing them into the caramel.

Bake at 325 degrees F for 12 minutes then Broil just until marshmallows begin to brown. Cool in pan on a wire rack. Use foil to lift uncut bars out of pan and onto a cutting board. Cut into bars and enjoy!