HEAT oven to 425°F.
BEAT 1/2 cup milk, sour cream and 3 Tbsp. sugar in large bowl with whisk until well blended. Stir in baking mix just until moistened. Spread onto bottom of greased 9-inch round pan. Bake 12 to 15 min. or until golden brown. Cool in pan 5 min. Remove cake from pan to wire rack; cool completely.
BEAT pudding mix and remaining milk in medium bowl with whisk 2 min. Stir in half the COOL WHIP. Toss strawberries with 1/3 cup sugar.
CUT cake horizontally in half to make 2 layers; stack on plate, filling with half the strawberry mixture and all the pudding mixture. Top with remaining COOL WHIP and strawberry mixture. Serve immediately.