Using a sharp knife, score the duck skin (fat) with diagonal parallel slashes 1/2 inch apart to make a diamond pattern, being careful not to pierce through to the flesh.
Pour the balsamic vinegar into a shallow dish just wide enough to fit the breasts in one layer.
Add the duck, flesh (not fat) side down; cover and leave to marinate for 20 minutes at room temperature (can be marinated up to 2 hours refrigerated but remove for last twenty minutes at room temperature).
Cherry Balsamic Vinegar Reduction
Add 4 oz. of black cherry fruit spread, sweetened only with fruit juice.
Pour chicken broth and most of the vinegar into a saucepan over med-low heat.
Add fruit spread and reduce for about half an hour, or until it’s reduced by about 2/3. When duck is sliced, add the extra juices to your sauce.
Recipe by Cooking Buffalo at http://cooking-buffalo.com/easy-duck-breasts-recipe-with-balsamic-vinegar-with-a-cherry-reduction/