Mushroom Swiss Burger Onions (Printable version)

A juicy beef patty with Swiss cheese, sautéed mushrooms, and caramelized onions on toasted buns.

# Ingredient List:

→ Burgers

01 - 1.5 lbs ground beef (80/20 blend recommended)
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 sliced onions, salt, and sugar if using. Cook, stirring occasionally, for 15 to 20 minutes until onions turn deep golden and caramelized. Lower heat if onions brown too quickly. Set aside.
02 - In a medium skillet over medium-high heat, melt butter and olive oil. Add mushrooms and cook for 4 to 5 minutes until browned. Stir in garlic, salt, pepper, and thyme if using; cook 1 to 2 minutes more. Remove from heat.
03 - Combine ground beef with salt, pepper, and Worcestershire sauce in a bowl. Gently mix then shape into four equal patties slightly larger than the buns.
04 - Heat a grill or skillet to medium-high. Cook patties 3 to 4 minutes per side for medium doneness, or longer as desired. In the last minute, top each patty with Swiss cheese and cover to melt.
05 - Lightly toast the buns on the grill or in a toaster until golden.
06 - Spread mayonnaise or aioli on the bottom bun if using. Layer lettuce, burger patty, sautéed mushrooms, and caramelized onions. Cap with the top bun and serve immediately.

# Expert Suggestions:

01 -
  • The caramelized onions add a sweet depth that makes every bite feel gourmet without any fuss.
  • Swiss cheese melts perfectly over the patty, creating creamy pockets that blend with the savory mushrooms.
  • It comes together in under an hour but tastes like you spent all day in the kitchen.
  • You can customize it easily—swap the beef, skip the bun, or add your favorite toppings.
02 -
  • Don't rush the onions—they need time and low heat to caramelize properly, or they'll burn and turn bitter.
  • Let the mushrooms sit undisturbed in the pan for a minute or two so they get a nice sear instead of steaming.
  • Make a shallow dimple in the center of each patty before cooking to prevent it from puffing up into a dome.
  • Use a lid or foil tent in the last minute of cooking to help the Swiss cheese melt evenly over the burger.
03 -
  • Cook the onions ahead of time and store them in the fridge—they reheat beautifully and save you time on burger night.
  • Don't press down on the patties while they cook, or you'll squeeze out all the flavorful juices.
  • If you're cooking for a crowd, keep the finished patties warm in a low oven while you work through the batch.
  • Toast the buns cut-side down in the same pan you cooked the burgers in—they'll soak up a little of that savory flavor.

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