Smash Burger Recipe

In a small bowl, combine mayonnaise, ketchup, Dijon mustard, sweet pickle relish, apple cider vinegar, garlic powder, smoked paprika, and salt. Whisk until smooth. Taste and adjust acidity or sweetness with a little more vinegar or relish if desired. Refrigerate while preparing other components so flavors meld (at least 10 minutes).

Clean mushrooms with a damp paper towel and slice thinly.

Heat a large skillet over medium-high heat. Add butter and olive oil. When butter foams, add mushrooms in a single layer (work in batches if necessary) and leave undisturbed for 90 seconds to get color.

Stir and continue to cook until mushrooms release moisture and brown, about 4–5 minutes. Season with 1/4 tsp salt, 1/8 tsp black pepper and thyme (if using). Remove from heat and set aside.

Divide the 1 lb of ground beef into four loose 4 oz portions and gently roll into balls; do not overwork the meat.

Preheat a heavy skillet or cast-iron griddle over high heat until very hot (about 5 minutes). Brush the cooking surface with 1 tablespoon neutral oil and spread to coat.

Place two beef balls on the hot surface leaving space between them. Using a sturdy spatula or a burger press, smash each ball firmly and evenly to about 1/4-inch thickness. Hold pressure for 10–15 seconds to create a good crust. Sprinkle each patty with a pinch (about 1/4 tsp total per patty) of kosher salt and a light grind of black pepper.

Cook without moving until edges are deeply browned, about 2–3 minutes. Flip patties and immediately top each with a slice of Swiss cheese. Cook another 30–60 seconds until cheese begins to melt and the patties are cooked through.

While patties are cooking, butter the cut sides of the buns with softened butter.

Toast buns: place cut-side down on the hot skillet or griddle for 30–45 seconds until golden and crisp. Remove and keep warm.

To assemble each smash burger: spread about 1 tablespoon house sauce on the bottom bun. Place one cheesy patty on the sauce, spoon about 2–3 tablespoons of sautéed mushrooms over the patty, then sprinkle about 2 tablespoons of crispy fried onions. Add a second cheesy patty if you prefer a double; otherwise top with the top bun. Spread a thin layer of sauce on the top bun if desired.

Serve immediately while hot so the cheese is melty and the onions remain crispy.