Mushroom Swiss Burger Onions (Printable)

Juicy beef patty with Swiss cheese, sautéed mushrooms, and sweet caramelized onions on toasted buns.

# What You'll Need:

→ Burgers

01 - 1.5 lbs ground beef (80/20 blend)
02 - 1 tsp kosher salt
03 - 0.5 tsp freshly ground black pepper
04 - 1 tbsp Worcestershire sauce

→ Caramelized Onions

05 - 2 large yellow onions, thinly sliced
06 - 1 tbsp unsalted butter
07 - 1 tbsp olive oil
08 - 0.5 tsp salt
09 - 1 tsp sugar (optional)

→ Sautéed Mushrooms

10 - 8 oz cremini or button mushrooms, sliced
11 - 1 tbsp unsalted butter
12 - 1 tbsp olive oil
13 - 1 clove garlic, minced
14 - 0.25 tsp salt
15 - 0.25 tsp black pepper
16 - 1 tsp fresh thyme leaves (optional)

→ Assembly

17 - 4 slices Swiss cheese
18 - 4 brioche or hamburger buns, split and toasted
19 - 4 tbsp mayonnaise or aioli (optional)
20 - Lettuce leaves (optional)

# How to Make It:

01 - Melt butter and olive oil in a large skillet over medium heat. Add onions, salt, and sugar if using. Cook, stirring occasionally, for 15 to 20 minutes until onions turn deeply golden and caramelized, reducing heat if browning too quickly. Set aside.
02 - Heat butter and olive oil in a medium skillet over medium-high heat. Add mushrooms and cook 4 to 5 minutes until browned. Stir in garlic, salt, pepper, and thyme if desired; cook an additional 1 to 2 minutes. Remove from heat.
03 - Combine ground beef, salt, pepper, and Worcestershire sauce in a bowl and mix gently. Shape mixture into four equal-sized patties slightly larger than the buns.
04 - Preheat grill or skillet to medium-high heat. Cook patties 3 to 4 minutes per side for medium doneness, longer if preferred. Place a slice of Swiss cheese on each patty during the last minute; cover to melt.
05 - Lightly toast the split buns on the grill or in a toaster until golden.
06 - Spread mayonnaise or aioli on the bottom bun if using. Add lettuce, then the burger patty, followed by sautéed mushrooms and caramelized onions. Top with the bun crown and serve immediately.

# Expert Advice:

01 -
  • The caramelized onions add a sweet, savory depth that makes every bite feel gourmet without any complicated techniques.
  • Swiss cheese melts beautifully over the hot patty, creating creamy pockets that mingle with the mushrooms and onions.
  • Its impressive enough for guests but simple enough to pull off on a busy evening when you want something better than takeout.
02 -
  • Dont rush the onions, low and slow is the only way to coax out their sweetness without burning them into bitterness.
  • Press a shallow dimple into the center of each patty before cooking to prevent it from puffing up into a meatball shape on the grill.
  • Let the mushrooms sit undisturbed in the pan for the first minute or two so they can actually brown instead of steaming in their own moisture.
03 -
  • Use a cast iron skillet if you have one, it holds heat beautifully and gives the patties a gorgeous crust.
  • Season generously right before cooking rather than mixing salt into the meat ahead of time, this keeps the texture tender instead of dense.
  • If youre grilling, oil the grates well and resist the urge to press down on the patties, that just squeezes out all the flavorful juices.

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