Mushroom Swiss Burger Onions (Printable)

A juicy burger stacked with earthy mushrooms, melted Swiss cheese, and sweet caramelized onions on a toasted bun.

# What You'll Need:

→ Caramelized Onions

01 - 2 large yellow onions, thinly sliced
02 - 2 tablespoons unsalted butter
03 - 1 tablespoon olive oil
04 - 0.5 teaspoon salt
05 - 1 teaspoon sugar (optional)

→ Mushrooms

06 - 9 ounces cremini or button mushrooms, sliced
07 - 1 tablespoon unsalted butter
08 - 1 tablespoon olive oil
09 - 0.25 teaspoon freshly ground black pepper
10 - 0.25 teaspoon salt
11 - 1 teaspoon fresh thyme leaves (optional)

→ Burgers

12 - 1.3 pounds ground beef (80/20 blend recommended)
13 - 1 teaspoon salt
14 - 0.5 teaspoon black pepper
15 - 4 slices Swiss cheese
16 - 4 brioche or hamburger buns
17 - 1 tablespoon unsalted butter (for toasting buns)

→ Toppings & Condiments

18 - 4 leaves lettuce
19 - 4 tomato slices
20 - 2 tablespoons mayonnaise (optional)
21 - 1 tablespoon Dijon mustard (optional)

# How To Make:

01 - Melt butter and olive oil in a large skillet over medium-low heat. Add sliced onions and salt. Cook, stirring occasionally, for 20 to 25 minutes until onions are deeply golden and soft. Optionally stir in sugar for added sweetness. Remove and set aside.
02 - In the same skillet, heat butter and olive oil over medium heat. Add mushrooms, salt, pepper, and thyme if using. Cook for 6 to 8 minutes until mushrooms are browned and tender. Remove and set aside.
03 - Divide ground beef into 4 equal portions and shape each into a patty slightly larger than the buns. Season both sides with salt and pepper.
04 - Preheat grill or skillet to medium-high heat. Cook patties 3 to 4 minutes per side for medium doneness. One minute before completion, place Swiss cheese slices atop patties, cover, and let melt.
05 - Spread butter on cut sides of buns and toast on grill or skillet until golden brown.
06 - Spread mayonnaise and Dijon mustard on bottom buns if desired. Layer with lettuce and tomato slices. Add burger with melted cheese, then spoon sautéed mushrooms and caramelized onions over. Cap with top bun and serve immediately.

# Expert Tips:

01 -
  • The caramelized onions and mushrooms do all the heavy lifting flavor-wise, so you can focus on getting the burger itself perfect.
  • It's fancy enough to impress someone at a dinner party but approachable enough for a regular Tuesday night craving.
  • The whole thing comes together in under an hour, which feels impossible given how elevated it tastes.
02 -
  • Do not skip the low heat for the onions; it's tempting to crank it up to save time, but you'll end up with burnt edges and a raw center instead of that sweet, melted texture.
  • Don't press down on the burgers while they cook—every time you do, you squeeze out the juice that makes them tender and flavorful.
  • The caramelized onions and mushrooms can be made an hour or two ahead, which means the actual burger assembly is just minutes of work.
03 -
  • Make the onions and mushrooms ahead of time and reheat them gently while your burgers cook; this keeps you from juggling five pans at once.
  • Keep your ground beef cold until the moment you cook it, and handle it as little as possible when forming patties—overworking it makes the burgers dense and tough.
  • Toast your buns even if it feels like an extra step; it keeps them from getting soggy and adds a textural contrast that matters.

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