French Onion Soup with Comté

Name: French Onion Soup with Comté
Ingredients: 4 tablespoons (½ stick) unsalted butter or duck fat; 6 large onions (about 5 lb.), thinly sliced; 2 large shallots, finely chopped; 2 garlic cloves, finely chopped; Kosher salt and freshly ground black pepper; ½ cup dry vermouth or dry white wine; 1 tablespoon white wine vinegar; 4 sprigs flat-leaf parsley; 2 sprigs thyme; 1 bay leaf; 8 cups low-sodium chicken or vegetable broth; 8 slices ¼-thick slices country-style bread, toasted; 8 ounces sliced Comté cheese or Gruyère