Marbled White Chocolate Brownie Dip

Store remaining brownie mix (from 13x9-inch family-size package) in resealable plastic bag at room temperature. Use to prepare additional dip at a later time. Or, empty remaining brownie mix into medium bowl. Add 1/4 cup oil, 4-1/2 tsp. water and 1 egg; mix well. Pour into foil-lined 8x5-inch loaf pan sprayed with cooking spray. Bake in 350°F oven 25 to 28 min. or until toothpick inserted in center comes out with fudgy crumbs. (Do not overbake.) Cool completely. Use foil handles to remove brownie from pan before cutting to serve.