In a saucepan, add 6 oz. blackberries and ¼ cup orange juice. Use a potato masher to break apart the berries, and give it a stir.
Add 2 tbsp. of balsamic vinegar.
Add 2 tbsp. of sugar. Turn heat to LOW and simmer for 12-15 minutes, stirring occasionally, until nicely reduced.
Push sauce through a mesh strainer to remove the seeds. Place it in a container and refrigerate until ready to serve.