French Dip Sandwiches

2 loaves French bread, sliced in half horizontally
¼ c. butter
1-2 lb. thinly sliced roast beef
8 oz. thinly sliced provolone cheese
2 cans beef consomme
1 large onion, sliced thin
2 c. water

Heat oven to 325 degrees. Spread butter evenly on top halves of bread. On bottom bread halves, layer roast beef and top with cheese; put two halves back together. Wrap each loaf in foil. Bake 25 minutes or until cheese is melted, then slice each loaf in quarters. Meanwhile, saute onion in a medium saucepan until tender. Add consomme, and water. Bring to a boil and simmer for 10 minutes. Pour the soup into 4 custard cups or small bowls and serve with the sandwiches for dipping.