Mushroom Burger Recipe

Prepare ingredients: clean mushrooms with a damp towel and slice about 1/4" thick. Thinly slice the yellow onion. Measure out butter, oil, thyme, Worcestershire, salt and pepper.

Heat a 10" skillet over medium-high heat until hot. Add the butter and olive oil; once butter foams, add the sliced onions. Cook, stirring occasionally, 3–4 minutes until they start to soften and turn translucent.

Add the sliced mushrooms to the skillet and spread into an even layer. Avoid overcrowding; cook without moving for 1–2 minutes to develop color, then stir. Continue cooking 4–6 minutes more until mushrooms are browned and onions are caramelized.

Stir in the Worcestershire sauce and thyme, season with 1/2 tsp kosher salt and 1/4 tsp black pepper. Cook another 30–60 seconds to combine flavors. Remove from heat and keep warm while you cook the patty.

Form the patty: gently shape the 8 oz (0.5 lb) ground beef into a round patty about 3/4"–1" thick, making a shallow dimple in the center with your thumb to prevent excessive doming while cooking. Handle meat lightly — do not overwork.

Season both sides of the patty with 3/4 tsp kosher salt and 1/2 tsp freshly ground black pepper just before cooking.

Heat a grill, cast-iron skillet or plancha over high heat. Brush the cooking surface with 1 tbs neutral oil and allow it to get very hot (surface should be shimmering but not smoking heavily).

Place the patty on the hot surface. For medium-rare to medium (recommended for an 8 oz burger), cook 3–4 minutes on the first side without moving to develop a crust.

Flip the patty and cook 3–4 minutes on the second side for medium doneness. In the last 60–90 seconds of cooking, place a slice of Swiss cheese on the patty and cover loosely with a lid or tent with foil to melt the cheese.

Remove the patty from the heat and let it rest on a plate for 2 minutes while you toast the bun and finish toppings.

Heat a small skillet or the grill to medium. Spread 1/2 tbs softened butter on cut sides of the bun. Toast buttered sides down until golden and crisp, about 1–2 minutes.

Place the toasted bottom bun on a plate, top with optional mayonnaise and Dijon mustard if using.

Place the rested beef patty with melted Swiss cheese on the bottom bun.

Top the patty with a generous scoop (about 1/2 cup) of the warm sautéed mushrooms and onions, spreading evenly.

Add optional lettuce, tomato slice and pickles as desired. Cover with the toasted top bun.

Serve immediately with your choice of side (fries, salad).