Slice the onions into rings and saute in butter in a skillet until tender. Turn crock pot on to low and put in the cans of beef broth, bay leaves, dash of garlic powder and salt and pepper, 2 tablespoons of worchestershire sauce, and 3/4 cup of water. When the onions and butter mixture is tender then also add them to the crock pot. Cover and cook for at least 3-5 hours on low. At this point you may want to taste the soup and see if you would like it a little weaker--if so add a little water or chicken broth. Also, at this time remove the bay leaves and discard them. When about ready to serve, slice bread into thin slices and toast in oven on 350 or in toaster oven until just crusty. Put toasted slices (1-3) in bowl and cover with the cheese (adjust cheese to your liking). Then cover bread and cheese with hot soup. The cheese will melt and the bread will rise to the top.