Preheat oven to 350, Prepare a 14" pizza pan with cooking spray; set aside. Prepare brownie mix batter according to package directions; stir in crushed cookies. Spread batter in prepared pan. Bake for 18 minutes or until done. Sprinkle marshmallows over top of hot brownie. Bake for three minutes more or until marshmallows are lightly browned. Sprinkle with nuts and candy, pressing lightly into softened marshmallows. Cool slightly on wire rack. Cut into wedges. Serve warm or cooled.