1Heat oven to 350°F (325°F for dark or nonstick pan). Grease or spray bottom and sides of 13x9-inch pan. In large bowl, stir together dry cake mix, butter, water, brown sugar and egg until well blended. Stir in nuts; spread in pan.
2Bake 20 minutes. Sprinkle with marshmallows. Bake 10 to 15 minutes longer or until marshmallows are puffed and golden. Sprinkle with candies.
3In small microwavable bowl, microwave frosting uncovered on High 10 to 15 seconds. Drizzle over bars. Cool completely, about 1 hour. For easier cutting, use plastic knife dipped in hot water. For bars, cut into 6 rows by 4 rows. Store loosely covered.