Heat oven to 350°. Grease a 9-inch springform pan. In large bowl, beat 1/2 cup sugar and the butter. Add 1 egg and 1 teaspoon vanilla; beat until creamy. Gradually add flour and baking powder, beating until smooth. Stir in 1/2 cup chocolate chips. Press onto bottom of prepared pan. In medium bowl, stir together sour cream, remaining 1/2 cup sugar, remaining 2 eggs and remaining 1 teaspoon vanilla. Stir in remaining 1/2 cup chocolate chips. Pour into pan. Bake 50 to 55 minutes, until almost set and edges are lightly browned. Cool completely on wire rack; remove sides of pan. Spread whipped topping over top. Cover; refrigerate. Just before serving, arrange strawberry halves on top of cake; garnish as desired. Refrigerate leftover dessert. Makes 12 servings.