1. Peel and slice the onions in half. Then cut into thin strips. 2. Melt the butter in a large soup pot. Add in the sliced onions and the thyme. For the next half hour, on medium heat, allow the onions to slowly soften. They will need to be stirred every five minutes or so to ensure they don't burn. If they become to sticky, add in a few more tablespoons of butter. 3. Once the onions are dark and sticky, add in the bay leaves, chicken stock, and beef stock. Stir and bring to a simmer. Add in the balsamic vinegar. 4. Cover and allow the soup to simmer for 20 minutes. Salt and pepper to taste. I tend to over pepper this soup because it adds a nice spice. 5. Dish up the soup into oven-safe ramekins. Top each ramekin with a piece of crusty bread and sprinkle the cheese evenly over the bread. 6. Place all the ramekins onto a baking sheet. Bake in a 450 degree oven for about 5-10 minutes or until the bread is golden and the cheese has melted.