Chicken Blackberry Vinegar

Saute chicken and remove from pan. Drain fat and deglaze pan with blackberry vinegar. Add the chicken and demi-glace. Bring to a boil. Finish with the butter. Remove chicken to serving plates and cover with sauce. Blackberry Vinegar 1 part blackberries 2 parts white vinegar Soak the blackberries in the vinegar for 3 hours, then pass the mixture through a food mill. Discard the seeds. Demi-glace 5 pounds beef bones 5 pounds chicken bones 1 half-bunch celery 1 carrot 1 - 2 onions 1 bay leaf 2 - 4 cloves garlic 1 pinch thyme 1 cup tomato puree Brown beef bones and boil. Keep covered with water for 8 to 10 hours. Strain, reserving liquid. Put beef bones in pot with chicken bones, vegetables and seasonings. Cover with water and cook 4 to 5 hours. Strain. Reserve liquid. Combine the second liquid with the first. Add tomato puree. Strain. Reduce until liquid will coat a spoon. Skim throughout reduction. Note: Reduction works best in a tall pot on low heat. Refrigerate between steps to bring fat to top and strain. Leftover demi-glace may be frozen in ice cube trays for future use.