Restaurant-Style French Onion Soup
1 cup red wine 1 French baguette, cut into 1/2-inch thick sl… 1 tablespoon sherry 1 teaspoon dried thyme 2 cloves garlic, crushed 2 quarts beef broth 2 tablespoons all-purpose flour 6 slices provolone cheese 6 slices Swiss cheese 8 onions, sliced olive oil, or as needed ½ cup butter ½ teaspoon ground black pepper, or to taste ½ teaspoon salt, or to taste