You can prepare this the day before serving, then refrigerate and bake when needed.

3 large Vidalia onions, sliced at least 1/4-inch thick
1/2 to 1 pound fresh mushrooms, sliced
1 can cream of mushroom soup
1 small can evaporated milk
1 tablespoon soy sauce
8 ounces or more shredded Swiss cheese
1 large loaf French bread, sliced

Saut?half of the onion and fresh mushrooms at a time just until soft - do not over-cook.

Mix together mushroom soup, milk and soy sauce. In a casserole, place half of the onion mixture then half of the soup mixture. Top with remaining half of onion mixture. Top with half of the cheese. Top with slices of French bread. Top with remaining half of soup mixture. Top with remaining cheese. Cover and bake at 325 degrees F for 30 minutes, then uncover and bake an additional 15 minutes.