1/4 c. butter
1 c. brown sugar
3 tbsp. cornstarch
2 c. water
1 tbsp. lemon juice
2 tbsp. vanilla
Rum or rum extract, to taste

Bring butter and sugar to a boil. Mix cornstarch with water; stir into butter and sugar mixture. Boil and stir until thickened. Add lemon juice, vanilla and rum or rum extract.