Brown the beef bones in a large roasting pan in the oven at 375 F until the bones are browned Cover with water and bring the mixture to a boil. Keep covered with water for 8 to 10 hours, simmering over medium to low heat. Strain, reserving liquid. Put beef bones in a pot with the chicken bones, vegetables and seasonings. Cover with water and cook 4 to 5 hours. Skim off any fat during the simmering. Strain. Reserve liquid. Combine the second liquid with the first. Add tomato puree. Strain. Reduce, simmering, until liquid will coat a spoon. Skim throughout the reduction. Note: Reduction works best in a tall pot on low heat. Refrigerate between steps to bring fat to the top and strain. Leftover demi-glace may be frozen in ice cube trays for future use. Source: Great Chefs of New Orleans, Tele-record Productions : Box 71112, New Orleans, Louisiana - 1983 : Chef Gerhard Brill, Commanders Palace Restaurant, New Orleans