French Onion Chicken

Ingredients (15)

• 2 tablespoons olive oil
• 4 tablespoons salted butter
• 2 sweet yellow or white onions, sliced into thin rounds
• 1 teaspoon granulated sugar
• 1/2 teaspoon coarse sea salt
• 2 to 3 sprigs fresh thyme removed from stems (plus more for garnish)
• 1 bay leaf
• 1 to 2 cloves garlic minced
• 4 boneless skinless chicken breasts (6 ounces each)
• 1/2 teaspoon black pepper
• 1 tablespoon all-purpose flour
• 1/2 cup dry white wine like a sauvignon blanc, optional
• 1 cup beef stock
• 1/4 pound provolone cheese grated (about 1 cup)
• 1/4 pound swiss cheese grated (about 1 cup)