- 10 minutes
- 9 hours
- 6 to 8
- Place the butter and the onion slices in a large slow cooker, along with the sugar. Stir the ingredients, cover the slow cooker, and cook on high for approximately 1 hour, stirring occasionally.
- Add the salt, pepper, onion soup mix, water, and beef broth, then stir well. Continue to cook on low heat for about 8 hours or on high heat for 4 hours.
- Butter each slice of the French bread, top with the Mozzarella and Parmesan, and place on a baking sheet. Broil the bread for one to two minutes, then serve a slice or two with each bowl of soup.