Kg Cheeseburger** Recipe

In a small bowl combine mayonnaise, ketchup, yellow mustard, sweet pickle relish, apple cider vinegar, sugar, and hot sauce (if using). Whisk until smooth and refrigerate for at least 10 minutes to meld flavors.

Slice the half onion into thin rings or half-moons. Heat 1 tablespoon olive oil in a skillet over medium heat. Add onions and a pinch of salt and cook, stirring occasionally, until soft and browned, about 8–10 minutes.

If using mushrooms, add sliced mushrooms to the pan after the onions are partly softened and cook together until mushrooms release moisture and turn golden, another 4–5 minutes. Remove from heat and set aside.

Preheat oven and prepare fries according to package directions (usually 425°F / 220°C). Toss frozen fries with 1 tablespoon vegetable oil and spread in a single layer on a baking sheet. Bake until golden and crispy, 18–25 minutes, flipping halfway. Season immediately with 1/2 tsp kosher salt.

Divide the 1/2 lb ground beef into two equal 1/4 lb balls. Gently form each ball into a loose patty about 4 inches wide and 1/2 inch thick. Do not overwork the meat. Lightly season both sides with 1 tsp kosher salt and 1/2 tsp freshly ground black pepper (split between patties).

Heat a heavy skillet or cast-iron pan over medium-high heat until very hot. Add 1 tablespoon unsalted butter (or a neutral oil) and let it melt and foam.

Place the patties in the pan, pressing down lightly with a spatula to create a thin, even contact (for a slight smash-style sear). Cook without moving for 2–3 minutes until the edges brown and juices collect on top.

Flip the patties and immediately place an American cheese slice on each patty. Cook another 1–2 minutes until cheese begins to melt and the patties reach desired doneness (about medium). If you want the cheese extra-melted, cover the skillet for 30–45 seconds.

While the patties finish, split the brioche buns and spread a thin layer of butter on cut sides. Place cut-side down on a separate pan or the oven broiler and toast until golden (about 1–2 minutes) — watch carefully to avoid burning.

To assemble each double-stacked burger: spread about 1 tablespoon secret sauce on the bottom bun. Place one cheese-topped patty on the sauce, then add a small handful of grilled onions (and mushrooms if used). Stack the second patty on top. Add 2 slices tomato and 1–2 lettuce leaves. Spoon another 1 tablespoon secret sauce on the top bun and close the burger.

If using optional add-ons: lay 2 cooked bacon strips across the first patty before stacking, or scatter 2 tablespoons crumbled blue cheese on top of the hot patty to begin melting, or add avocado slices to the top of the second patty.

Serve the assembled cheeseburger immediately with a generous portion of fries on the side.