1/2 c. plus 3 tbsp. butter, softened
1 1/3 c. sugar
8 egg whites
1/2 c. nonfat sour cream
1/3 c. evaporated skim milk
2 tsp. vanilla extract
1 1/3 c. flour
1 tsp. baking powder
1/2 tsp. salt
2/3 c. unsweetened cocoa
Vegetable cooking spray

Beat butter at medium speed of an electric mixer until fluffy; gradually add sugar and beat well. Add egg whites, sour cream, milk and vanilla; beat well. Combine flour and next 3 ingredients; stir well. Add flour mixture to creamed mixture, mixing well. Pour batter into a 13 x 9 x 2-inch baking pan coated with cooking spray.

Bake at 350°F for 25 minutes or until a wooden pick inserted in center comes out clean. Cool in pan on a wire rack. Spread your favorite creamy chocolate frosting over cooled brownies and cut into squares.