Balsamic Sauce

Grrrrrgh!
Course : Italian
From: HungryMonster.com
Serves: 4
 

Ingredients:

1 cup balsamic vinegar
4 cloves garlic
4 pinches fresh rosemary
2 tablespoons butter -- optional
 

Preparation:

Put all the ingredients except the butter into a saucepan and bring to a boil. Reduce the heat and simmer until it is reduced by half, about 10 minutes. The sauce is ready when it coats the back of a spoon. Add the optional butter and stir well.