HEAT oven to 425°F. Beat 1/2 cup milk, sour cream and 3 Tbsp. sugar in large bowl with whisk until well blended. Add baking mix; stir just until moistened. Spread onto bottom of greased 9-inch round pan. Bake 12 to 15 min. or until golden brown. Remove 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; set aside. Cut cake horizontally in half.
PLACE bottom cake layer on plate; top with half the strawberries. Spread with pudding mixture; cover with top cake layer. Spread with remaining Cool Whip; top with remaining strawberries. Serve immediately. Refrigerate leftovers.