Blackberry Reduction

2 - 3 C Blackberries (fresh or frozen)
½  stick of salted butter, cut into 4ths
½ to 1 C Sugar
½ to 1 tsp  Balsamic Vinegar

In a medium sauce pan, on medium heat, add blackberries and butter.  The butter will completely melt and the blackberries will start to become very juicy.  Let simmer for about 5 min. after butter has melted.  Stir in desired amount of sugar.  Sugar should melt pretty quickly and the berry juice should start to thicken up.  Splash with desired amount of balsamic vinegar.   Pour berries into a strainer over a bowl in order to sift out seeds.  Serve warm or cold. Refrigerate leftovers.

From All About Cooking, Food and Stuff