French Onion Soup — Three Many Cooks

Ingredients

• 2 tablespoons each: butter and olive oil, plus extra oil for brushing bread
• 4 large sweet onions (about 2½ pounds), halved and sliced thin
• 1 quart chicken broth
• 2 tablespoons flour
• ¼ cup sweet vermouth
• 18½-inch slices cut from a baguette
• 6 slices Swiss or Provolone cheese, about 4 ounces
• 6 tablespoons grated Parmesan cheese