This stuff is so good you could drink it....wait, I think I have!
1 c. sugar
1/2 c. butter, 1 stick
1/2 c. buttermilk (I use 1/2 c. water and 2 Tbsp. buttermilk powder)
Scant 1/8 tsp. baking soda
1 tsp. vanilla
In a small bowl, whisk together dry ingredients (including buttermilk powder).
In saucepan, bring butter and buttermilk (or water) to a boil. Pour dry ingredients into saucepan, stirring constantly! Re-bring to boil and stir for a minute or two. It will thicken as it cools. Take off heat and stir in vanilla.