1/4 cup Buttermilk
1/2 cup Sugar
1/4 cup Butter or margarine
1 1/2 tsp Cornstarch
1/4 tsp Baking soda
1 1/2 tsp Vanilla extract
Combine buttermilk, sugar, butter, cornstarch, and baking soda in a small saucepan. Bring mixture to a boil.
Cool slightly, and stir in vanilla extract.
Pour over top while both are still warm.