French Onion Soup for Two

Name: French Onion Soup for Two
Prep time: 15 min
Cook time: 1 h 15 min
Total time: 1 h 30 min
Cuisine: French
Ingredients: 1 tablespoon olive oil; 4 tablespoons unsalted butter; 2 large yellow onions (about 2 pounds, halved and thinly sliced (8-9 cups)); 1/2 teaspoon salt; 1 bay leaf; 2 sprigs fresh thyme; 4 cloves garlic (minced); 1 tablespoon all-purpose flour; 1/2 cup dry red wine; 4 cups beef broth or stock (preferably low sodium); 1 to 2 tablespoons dry white wine or dry sherry (optional and if needed); Freshly ground black pepper (to taste); 1 small sourdough baguette (sliced into 4 thick pieces, ends discarded); 1/4 pound grated Gruyere cheese