Crockpot French Onion Soup

Bahan-bahan (8 porsi)

• 3 large white onions (sliced)
• 3 tablespoons butter
• 64 ounces beef broth (I use reduced sodium)
• 1 tablespoon Worcestershire sauce
• 1 clove garlic (minced)
• ⅓ cup dry sherry
• 4 sprigs fresh thyme (or 1 teaspoon dried thyme)
• 1 bay Leaf
• 8 slices French bread (* stale or dry is best)
• ¾ cup shredded Gruyere cheese
• ½ cup shredded Emmental cheese
• 6 tablespoons shredded Parmesan cheese