Caramel Topping for a Coffee Cake

Stir up a standard yeast coffee cake dough and let rise in pan. When risen pour a mixture of the following over the top.

1 cup firmly packed brown sugar
1/2 cup sour cream
2 tsp. cornstarch
1/2 tsp. vanilla

Bake in 350 degree oven for 30 to 35 minutes. Serve warm.