Ingredients:
6 medium sweet onions, thinly sliced
1 clove garlic, minced
2 Tbsp butter, unsalted
2 can(s) beef broth, 14 ounce
2 tsp Worcestershire sauce
1/4 tsp freshly cracked black pepper, or to taste
8 slice french bread, 1 inch thick
8 slice swiss or gruyere cheese
1/4 c dry sherry, if desired
Directions:
1. In a large skillet, cook onions and garlic on low heat in hot butter for about 20 minutes and stir several times.
2. Transfer onion mixture to a 5-quart crock pot. Add beef broth, Worcestershire sauce and 1 cup water. Cover and cook on low for 6 hours or on high for 3 hours.
3. Before serving soup, toast bread slices with cheese slice on top. (Broil for 3 minutes or until cheese is light brown and bubbly).
4. Ladle soup into bowls and top with toast
source:https://www.spendwithpennies.com/slow-cooker-french-onion-soup/