Onion Soup with (or without) Cheese Croutes — Ronnie Fein

Ingredients

• oil
• 2 pounds yellow onions, peeled and sliced
• 3/4 teaspoon salt, or to taste
• 1/2 teaspoon sugar
• 1-1/2 tablespoons all-purpose flour
• 6 cups heated vegetable stock (or with beef stock if you serve without the croutes)
• 1/4 cup sherry, peferably Oloroso type