Brown the beef bones and put them in a large stockpot. Cover with water and boil. Keep the bones covered with water for 8 to ten hours. Strain, reserving the liquid. Put the beef bones in the pot with the chicken bones, vegetables and seasonings. Cover with water and cook for 4 to 5 hours. Strain, reserving the liquid. Combine both the beef liquid and the chicken liquid together. Bring to a boil and then add the tomato puree. Cook for 10 minutes, then strain. Increase heat and reduce until the liquid will coat a spoon. Skim the surface of the mixture throughout the reduction. Any leftover demi-glace can be frozen in an ice cube tray and used a cube at a time later.... Source: Great Chefs of New Orleans, Tele-record Productions : Box 71112, New Orleans, Louisiana - 1983 : Chef Roland Huet, Christians Restaurant, New Orleans