If there is a single dish that warms a Frenchman’s heart and soul, it’s soupe a l’oig-non gratinée — the ultimate Gallic comfort food, which, at its best, is a rich, dark brown broth teeming with sweet, caramelized onions beneath a raft of toast layered with an abundance of Gruyère cheese that is bubbling and browned when it comes to your table in the traditional little brown crock.

The steam, the aroma, and the need to wait till its searing heat dissipates before you even dare taste are all part of the appeal. In Paris, where every bistro serves it, the soup was once a standard menu item at the workingman’s eateries at the old Les Halles food market, where it is still at its classic best at the art deco Au Pied de Cochon (6 rue Coquillière; 011-33-1-40-13-7700). Fortunately, American chefs love this onion soup too, so here are some of the best places to find it prepared in all its gooey glory.

mimosa, 8009 beverly blvd., los angeles; (323) 655-8895
viognier, 222 e. fourth ave., san francisco; (650) 685-3727
l’absinthe, 227 e. 67th st., new york city; (212) 794-4950
sandrine’s, 8 holyoke st., cambridge, mass.; (617) 497-5300
bistro provence, 13616 memorial dr., houston; (713) 827-8008
bistro 110, 110 e. pearson st., chicago; (312) 266-3110