PREHEAT oven to 425°F. Beat 1/2 cup of the milk, the sour cream and 3 Tbsp. sugar in large bowl with wire whisk until well blended. Stir in baking mix until just moistened. Spread evenly into greased 9-inch round cake pan. Bake 12 to 15 min. or until top is golden brown. Remove from pan to wire rack; cool completely.
ADD remaining 3/4 cup milk to dry pudding mix in medium bowl. Beat with wire whisk 2 min. or until well blended. Gently stir in half of the whipped topping. Toss strawberries with 1/3 cup sugar; set aside. Cut cake horizontally in half to make two layers.
PLACE bottom cake layer on serving plate; top with half of the strawberry mixture. Spread with pudding mixture; cover with top cake layer. Spread with remaining whipped topping; top with remaining strawberry mixture. Serve immediately. Store any leftover shortcake in refrigerator.