Melt the butter in a large saucepan and sauté the onions over medium high heat for about eight minutes or until they are lightly browned.
Add broth, salt and pepper and boil gently for about 5-10 minutes.
Pre-heat the oven to 400°F. Place the baguette slices on a baking sheet and toast in the oven.
Place one or two slices of baguette in the bottom of each of four ovenproof crocks.
Next add approximately 1/4 cup of grated cheese to each crock.
Ladle the onion and stock mixture into the crocks.
Repeat with another layer of baguette, cheese, and onion, then top with the remaining grated cheese.
Bake for 15 to 20 minutes or until cheese is beautifully browned.