Mushroom Swiss Burger Caramelized Onions

There was a Saturday last spring when I decided regular burgers just weren't cutting it anymore. I had mushrooms wilting in the fridge and a block of Swiss cheese I kept forgetting about, so I threw them together on a whim. The smell of those onions cooking low and slow filled the whole apartment, and suddenly I was making something that felt like it belonged in a bistro, not my tiny kitchen.

The first time I made these for friends, someone asked if I'd ordered them from a restaurant. I didn't correct them right away because honestly, watching their faces when they took that first bite was too satisfying. One of them even scraped the leftover mushrooms and onions off the pan with a piece of bun, and I knew I'd stumbled onto something worth repeating.

Ingredients

• Ground beef (80/20 blend): The fat content is what keeps these burgers juicy and flavorful, so don't go leaner unless you want a drier patty.
• Yellow onions: They break down into sweet, golden strands when you cook them slow, and patience here is everything.
• Cremini or button mushrooms: I like cremini for their deeper flavor, but button mushrooms work just fine and brown up beautifully either way.
• Swiss cheese: It melts like a dream and has this nutty, mild flavor that doesn't overpower the beef or toppings.
• Worcestershire sauce: Just a tablespoon adds a savory, umami backbone to the meat without making it taste like anything other than a really good burger.
• Brioche buns: They toast up buttery and soft, and they hold up to all the toppings without falling apart in your hands.

Instructions

Caramelize the onions:

Melt the butter and oil together in a large skillet over medium heat, then add the sliced onions with salt and optional sugar. Stir them every few minutes and let them cook for 15 to 20 minutes until they turn a deep golden brown and smell almost sweet.

Sauté the mushrooms:

In another skillet over medium high heat, melt butter and oil, then toss in the mushrooms and let them cook undisturbed for a couple minutes to get a good sear. Add the garlic, salt, pepper, and thyme toward the end and stir for another minute or two until fragrant.

Shape the patties:

Gently mix the ground beef with salt, pepper, and Worcestershire sauce in a bowl, then form four patties that are slightly bigger than your buns since they'll shrink a bit while cooking.

Cook the burgers:

Heat your grill or skillet over medium high heat and cook the patties for 3 to 4 minutes per side for medium doneness. In the last minute, lay a slice of Swiss on each patty and cover the pan or close the grill lid so the cheese melts into a gooey layer.

Toast the buns:

While the cheese is melting, split the buns and toast them cut side down on the grill or in a toaster until they're lightly golden.

Assemble and serve:

Spread mayonnaise or aioli on the bottom bun if you like, add lettuce if you want some crunch, then stack the burger, mushrooms, and caramelized onions before topping it off with the bun. Serve right away while everything is still warm and melty.

Save

I remember making these on a Tuesday night when I was too tired to think straight, and somehow they still turned out perfectly. My partner took one bite and said it tasted like comfort, which is probably the best compliment a burger can get. It's become the thing I make when I want to feel like I'm treating myself without leaving the house.

Choosing Your Beef

I learned the hard way that lean ground beef makes for a sad, dry burger, so I always reach for the 80/20 blend now. The fat renders as it cooks and bastes the meat from the inside, which is what gives you that juicy, flavorful bite every time.

Getting the Onions Right

The first time I tried caramelizing onions, I gave up after ten minutes because nothing was happening. Now I know you really do need that full 15 to 20 minutes over medium heat, stirring every so often and letting them do their thing. If they start to stick, a splash of water loosens them right up and keeps the fond from burning.

Make It Your Own

Sometimes I add a splash of balsamic vinegar to the onions in the last few minutes for a tangy sweetness, or I swap the Swiss for Gruyere when I'm feeling fancy. You can also use ground turkey or chicken if you want something lighter, though I'd add an extra drizzle of oil to keep them moist.

• Try a smear of Dijon mustard on the bun for a sharp, peppery kick.
• If you don't have fresh thyme, dried works fine or you can skip it altogether.
• These pair beautifully with crispy fries, a simple salad, or even just some pickles on the side.

Save

This burger has become my go to whenever I want something that feels special but doesn't require a trip to the store or hours in the kitchen. I hope it becomes one of those recipes you reach for on a whim and end up making over and over again.