I have made this but much prefer the old fashioned(buttermilk) one.

1/2 cup butter
1 cup brown sugar (firmly packed)
1/4 teaspoon salt
1/2 cup milk
2 1/2 cups confectioner's sugar, sifted
1 teaspoon vanilla

Melt butter in a large saucepan. Blend in brown sugar and salt. Cook over low heat for two (2) minutes, stirring constantly. Add milk, continue stirring until mixture comes to a boil. Blend in confectioner's sugar gradually. Add vanilla, mix well. Thin with small amounts of cream if needed.