Ingredients :

• 15% Fat Ground Beef — Fat is the juice. With 5% fat, you’ll have a steak as dry as a shoe sole. 15% is the absolute minimum. If you go to the butcher, ask for a blend with a bit of marbled beef — but supermarket meat works just fine. And don’t form the balls in advance: do it just before putting them in the pan to prevent the meat from warming up and sticking.
• Brioche Bun — It must be toasted with butter — not for looks, but to create a barrier against the moisture of the sauce. An untoasted bun lasts 30 seconds before collapsing in your hand. Choose a standard size, not too thick, otherwise the bread-to-meat ratio goes the wrong way.
• Cheddar — Classic cheddar, not the ‘extra mature’ stuff which is too strong. It melts well and adds a slight lactic acidity that cuts through the richness of the meat. Alternatively, raclette works even better: it melts faster, forms a creamy veil over the steak, and its milky taste goes perfectly with the caramelized crust.
• Onion — One is enough for two burgers. Slice it thin — really thin, almost translucent — and sauté it after the steaks, directly in the remaining pan juices. In 3-4 minutes over high heat, it takes on an amber color like light honey and a sweetness you can’t get any other way.