French Onion Stuffed Chicken Casserole

Ingredients

• 4 boneless, skinless chicken breasts
• 1 tablespoon olive oil
• 2 tablespoons unsalted butter
• 1 cup shredded gruyere cheese
• 1/2 cup beef broth or stock
• 2 teaspoons garlic powder
• 4 tablespoons freshly grated parmesan cheese
• 2 tablespoons white wine, sherry or balsamic vinegar
• Pinch of salt and pepper
• 1 teaspoon ground thyme
• 4 large onions
• 2 cloves garlic
• 2 teaspoons fresh chopped thyme