Mushroom Swiss Burger Onions (Printable)

Juicy beef burger layered with sautéed mushrooms, Swiss cheese, and caramelized onions on toasted buns.

# What's Needed:

→ Burger

01 - 1 lb ground beef (80/20 blend preferred)
02 - 1 tsp kosher salt
03 - ½ tsp freshly ground black pepper
04 - 1 tsp Worcestershire sauce

→ Caramelized Onions

05 - 2 large yellow onions, thinly sliced
06 - 1½ tbsp unsalted butter
07 - 1 tbsp olive oil
08 - ½ tsp salt
09 - ½ tsp sugar

→ Mushrooms

10 - 8 oz cremini or button mushrooms, sliced
11 - 1 tbsp unsalted butter
12 - 1 clove garlic, minced
13 - ¼ tsp salt
14 - ¼ tsp black pepper
15 - 1 tsp fresh thyme leaves (optional)

→ Assembly

16 - 4 slices Swiss cheese
17 - 4 brioche or hamburger buns, split
18 - 2 tbsp mayonnaise (optional)
19 - Lettuce leaves (optional)

# How to Make It:

01 - In a large skillet over medium heat, melt butter with olive oil. Add sliced onions and sprinkle with salt and sugar. Cook, stirring frequently, for 20 to 25 minutes until onions are deeply golden and caramelized. Transfer to a bowl and set aside.
02 - Using the same skillet, melt butter over medium heat. Add mushrooms and cook until they release moisture and begin to brown, about 6 to 8 minutes. Add garlic, salt, pepper, and thyme if using; sauté for 1 to 2 minutes more. Set aside.
03 - In a bowl, gently mix ground beef with Worcestershire sauce, salt, and pepper. Divide mixture into 4 equal portions and shape into patties with a slight indent in the center of each.
04 - Preheat a grill or skillet over medium-high heat. Cook patties for 3 to 4 minutes per side for medium doneness or until preferred level is reached. During the last minute, place a slice of Swiss cheese on each patty and cover until melted.
05 - Lightly toast the bun halves on the grill or in a toaster until golden.
06 - Spread mayonnaise, if desired, on the bottom buns. Layer with lettuce leaves, the cooked patties topped with melted cheese, sautéed mushrooms, and caramelized onions. Cap with top buns and serve immediately.

# Tips for Success:

01 -
  • The caramelized onions bring a natural sweetness that feels indulgent without being heavy.
  • Melted Swiss cheese creates this creamy richness that elevates it beyond a basic burger.
  • You can prep the mushrooms and onions ahead, so assembly becomes the easiest part of dinner.
02 -
  • Don't mix the burger patties with an electric mixer or overwork them by hand—the second you see everything combined, stop, or you'll end up with hockey pucks instead of tender patties.
  • If your onions aren't browning after 15 minutes, increase the heat slightly; if they're browning too fast and the edges are burnt, lower it—every stove is different.
  • Let the burgers rest for a minute or two after cooking so the juices redistribute instead of running all over the plate.
03 -
  • If you have a meat thermometer, pull the burgers at 160°F for medium—this takes the guesswork out of doneness and prevents overcooking.
  • Don't press down on the burgers while they cook; you're just squeezing out the delicious juices and making them dry.

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