Bring to a boil, then lower the heat so the sauce is at a lively simmer. Cook, stirring occasionally, until the sauce is dense but juicy and a rich, dark red color. (Most likely a noticeable layer of oil will float to the top toward thee end of cooking). This will take about 2 to 3 hours..the longer you cook it, the better it will become. While the sauce is cooking, add hot water as necessary to keep the meats and vegetables covered. The oil can be removed with a spoon and reincorporated into the sauce which is done traditionally.
*the sauce can be made the day before and skim the fat off the top.