Grandma's Brown Sugar Icing

1            cup brown sugar
1/2        cup margarine
1/4        cup milk
1/2        tsp. vanilla
2/3-3/4 cup of icing sugar

• Bring brown sugar, margarine and milk to a roiling boil in a medium sized pot on med-high.  Boil for 2 minutes (start timing after it gets to the point that you can't 'stir away' the boil).
• Take off heat and add in vanilla and icing sugar.  Mix well. 
• Stir until starting to thicken and then pour over cake while icing is still warm.
•  Scrape leftover icing out of pot with a spoon, while kids and husbands are not looking, and EAT! (don't burn your tongue though or you may be forced to explain)