Parisians have tried to hijack French onion soup, but Lyonnais cooks can plausibly claim title to this bistro classic. A local traveler once observed, “After a meal of onion soup, sausage, a good Saint-Marcellin cheese, and a bottle of Juliénas, nothing more is needed but a good night’s sleep.” The same four specialties remain typical of Lyon. There are two keys to good onion soup: use pungent yellow onions, and cook them to a dark, almost burnt caramel for good depth of flavor. In this recipe, I have added my personal tip: a cut onion charred in a dry pan to add particular intensity and color.
Melt the butter in a soup pot over low heat. Stir in the sliced onions, season with salt and pepper, and press a piece of buttered aluminum foil down on the onions. Cover the pan and sweat the onions over very low heat, stirring occasionally, 20 to 25 minutes. Remove the lid and foil, raise the heat, and continue cooking, stirring occasionally to prevent scorching, until the onions are reduced, concentrated, and very dark brown, 8 to 10 minutes longer.
Meanwhile, char the halved onion. Heat an electric burner until hot, or heat a small sauté pan over a gas burner. Sprinkle the cut surfaces of the onion with the sugar and set the halves, cut side down, on the burner or pan. Cook until dark brown, 2 to 3 minutes.
When the sliced onions are ready, stir in the broth and add the charred onion. Cover, bring to a boil, and simmer to blend the flavors for 10 to 15 minutes. Discard the charred onion halves, taste the soup, and adjust the seasoning. The soup can be made 2 to 3 days ahead and stored in the refrigerator.
Preheat the broiler and reheat the soup if necessary. Put 4 to 6 deep flameproof soup bowls on a baking sheet and heat in the broiler. Set 2 or 3 croûtes in each bowl and ladle the soup on top. Sprinkle with the cheese and broil until the tops are browned. Serve at once — onion soup must be scalding hot.
© 2007 All rights reserved. Published by Chronicle Books.