In a deep, large kettle melt the butter over high heat until it just starts to boil.

Add the brown sugar.

Bring to a boil and lower heat to medium and continue to boil for 2 minutes.

Don't boil longer than two minutes and stir constantly while it is boiling.

Add the milk and splash of vanilla and return to a boil, stirring constantly.

As soon as it begins to boil, remove from heat and cool to lukewarm.

Gradually add confectioners' sugar.

Stir with a wooden spoon until thick and spreadable.