Easy Brownie Shortcake Dessert

1 pkg (19.5 oz) brownie mix
1 container (16 oz) sour cream, divided
1 cup thawed cool whip
1 Tbsp powdered sugar
1 tsp vanilla
3 cups cut up mixed strawberries and peeled kiwi

Preheat oven to 350 degrees.  Prepare brownie batter as directed on package; stir in 1/2 cup sour cream.  Spoon into greased and floured 9-inch round cake pan.  Bake 45 minutes; cool 10 minutes.  Remove from pan to wire rack and cool completely.  Mix remaining sour cream, whipped topping, sugar and vanilla.  Cut brownie horizontally in half.  Place bottom half on plate; spread with half of the sour cream mixture.  Cover with tip of brownie, remaining sour cream mixture and fruit.  Store in refrigerator.