Slow Cooker French Onion Soup

Ingredients (12)

• 6 sweet onions,
• 4 tablespoons unsalted butter,
• 1/4 teaspoon sugar
• 1/2 teaspoon salt
• 1/2 teaspoon fresh ground pepper
• 4 to 6 sprigs fresh thyme
• 1 bay leaf
• 6 cups fat free, low sodium beef broth
• 1/2 cup dry white wine
• salt and pepper,
• 6 slices french bread
• 1 1/2 cups shredded gruyere cheese, optional