In a mixing bowl, beat egg and half cup sugar. Combine flour, baking powder and salt; add alternately with milk to sugar mixture, beating well after each addition. Stir in butter. Fold in berries. Pour into a greased 8-in square baking pan; sprinkle with the remaining sugar. Cover and chill overnight. Remove from the refrigerator 30 minutes before baking. Bake at 180ºC or 30-35 minutes.