Chop up carcass coarsely. Add it to big soup pot with 2 quarts water and bring liquid to a boil, but don't let boil. Skim off fat and scum that will come to the top Lower the heat, add onion, carrot and cook, partially covered for 2 to 3 hours or until bones and vegetables have given up their flavor. Be sure to keep level of water constant. Strain, cool to room temp and refrigerate. Next day remove any fat that has come to the surface.