1/2 tsp. baking soda
1 c. buttermilk
2 c. granulated sugar
1/2 c. light brown sugar
1 stick butter
2 tbsp. white corn syrup

Dissolve soda in buttermilk. Combine all ingredients and cook over low heat until mixture forms a soft ball when tested in cold water. Remove from heat and beat to desired consistency. If mixture hardens too much for spreading, add a little milk or cream.