French Onion Soup Burgers

If you’re a fan of traditional French onion soup — and who isn’t? — you’re going to love this burger. It’s kitted out with all of the ingredients that make the soup such a treasure — tender, browned onions, beef broth, red wine, Gruyere cheese and French bread — and finally lathered up with mustard mayo. Rich and full of flavor, this burger is the perfect entrée for a Labor Day bash.

Prepping it, however, does require a bit of care. The onions need to be cooked low and slow so that they’ll soften and brown properly. (You can, however, cook them a full day ahead, then cover and chill them until the moment of truth.) Likewise, you want to keep a strict eye on the burgers as they cook. Overdo it and they’ll end up dry.

You’re welcome to buy whatever kind of burger strikes your fancy, but please resist the siren call of prepackaged quarter-pounders. They’re too thin for this recipe and will definitely end up overcooked. If you’re up for a little extra work, you can “grind” your own meat by buying the beef of your choice — skirt steak, short ribs, sirloin, you name it — cutting it into 1-inch cubes, freezing it for 40 minutes and finally pulsing it (in two batches) in a food processor until you reach the ground beef texture you desire.

Classic French onion soup calls for Gruyere cheese, but you’re free to swap in a different variety as long as it melts as well as Gruyere. Likewise, if you don’t want to add wine to the recipe, you can deglaze the burger pan with stock or water.

In the classic recipe, a slice of French bread is floated on the soup’s surface like a bowl-wide crouton. Here that bread provides the coziest of beds for a juicy burger. (In truth, though, that bread — lightly brushed with olive oil, browned in the oven and rubbed with garlic — is fairly amazing all by itself.)