Place meat, water, onion, bay leaf in pressure cooker. Cook 30 minutes, allow vent to cool down on its own. (Or, if preferred, double the amount of water and simmer in a heavy saucepot until tender, about 3 hours). Remove meat and reserve one cup of broth. Discard the onion and bay leaves. Cut and (or) shred beef into bite-sized pieces. In small pan melt butter, saute chopped onion until tender and golden.
Add all the remaining ingredients, along with the reserved broth, to the onions and simmer for 5-10 minutes. Pour sauce over meat. Simmer 30 minutes. Serve on rolls or bread. (Keeps well in a crockpot can be taken to picnics, potlucks, etc. Leftovers freeze well). Serves 10-12.