1 c. buttermilk
2 c. white sugar
1/2 c. dark brown sugar
1/2 tsp. baking soda
1/2 c. butter (1 stick)
1 tsp. vanilla

In large saucepan, combine buttermilk sugar and soda. Cook to softball stage (238 degrees F). Do not stir while mixture is boiling.

Add butter and cool 5 minutes. Beat at high speed until thick. Add vanilla, use cream to thin mixture if it sets up too quickly.