French Onion Chicken Soup

Ingredients

• 2 tbsp unsalted butter
• 1 tbsp olive oil
• 4 large yellow onions, thinly sliced
• 1 tsp salt
• 1/2 tsp black pepper
• 2 tsp granulated sugar (to help caramelize the onions)
• 3 cloves garlic, minced
• 1/2 cup dry white wine (optional, for deglazing)
• 4 cups beef broth
• 2 cups chicken broth
• 2 boneless, skinless chicken breasts (sliced or shredded)
• 1 tbsp fresh thyme leaves (or 1 tsp dried thyme)
• 2 tbsp Worcestershire sauce
• 1 bay leaf
• 4 slices French baguette (toasted)
• 1 cup Gruyère cheese, shredded
• 1/2 cup Parmesan cheese, grated
• 1 tbsp butter, for toasting bread