Mushroom Swiss Burger with Caramelized Onions
This post may contain affiliate links. Please read our disclosure policy.
Mastering a classic mushroom Swiss burger at home is a skill you’ll forever thank yourself for. I’ve tested dozens of versions over the years, and this one gets everything right: it’s meaty, melty, juicy, and so satisfying. I’ll walk you through exactly how to make a burger you’ll keep coming back to.
My husband still teases me about the road trip when I discovered my mushroom Swiss burger obsession. We stopped off at a tiny diner in the middle of nowhere – the type that has vinyl seats and records on the wall. We both ordered mushroom Swiss burgers – and I was hooked. I think I ate one every day for the next 3 days – call me predictable, but it’s a classic for a reason!
Since that trip, I love recreating the diner-style magic at home. I make this mushroom Swiss burger recipe at least once a month throughout the summer. I love how the umami mushrooms, sweet caramelized onions, and melty cheese all come together – with some crisp butter lettuce to contrast. This recipe is proof that simple ingredients and an easy method can make the best dinners.
Key ingredient notes
The magic of this burger is in its simplicity – no unexpected, fancy ingredients – just good old melty cheesy, caramelized onions, and buttery mushrooms. This is what you need:
- Burgers: Brioche buns and lean ground beef.
- Toppings: Caramelized onions, cremini mushrooms, Swiss cheese slices, and butter lettuce.
4 quick tricks for burger bliss
- Low and slow: Give your onions plenty of time to caramelize. Patience is the most important ingredient here! You want to unlock all the golden sweetness, and that takes time. If you’d like, check out my post on how to make caramelized onions for even more details!
- Mushrooms: Season the mushrooms after cooking. Salting them before you cook them pulls out their water, helping them stay firm and enhancing the flavors.
- Melted cheese: Adding the cheese in the final two minutes of the patty cooking helps it reach the perfect melt. Add it too soon – it becomes a mess, and add it too late, and it’s just, well, not melty enough!
- Toasting the hamburger buns: This step is one of those little things you can do to totally elevate your burger. Don’t forget to butter them up first!
I love serving these with my dill French fries and blue cheese coleslaw!
Make-ahead tips and how to store leftovers
- Burger patties: You can form your patties a day ahead. Store them in a covered container in the fridge, then cook them right before serving – they’re best cooked before assembling (that way they’re juiciest, and you can melt the cheese on them, too!)
- Toppings: The most time-consuming part of this recipe is caramelizing the onions, then sautéing the mushrooms. If you want to streamline things ahead of time, you can do this up to 3 days before, then store them separately in containers in the fridge. Warm them in a skillet before serving.
- Storage for leftovers: Let any leftovers cool to room temperature. Then, pack them away in a container and keep ithem n the refrigerator for up to 3 days.
Mushroom Swiss Burger with Caramelized Onions
Ingredients
- 1 ½ tablespoons butter (plus more for the buns)
- 2 large yellow onions (vertically sliced – see notes)
- 1 teaspoon salt (divided)
- 1 ½ lb lean ground beef
- 1 tablespoon olive oil
- 8 ounces crimini mushrooms (sliced)
- 4 thick slices swiss cheese
- 4 brioche buns
- Mayonnaise and butter lettuce
Instructions
- Melt the butter in a large, cast-iron frying pan over medium-high heat. As soon as it's melted, add the onions and stir. Cook for 8-10 minutes, stirring occasionally, until the onions have softened.1 ½ tablespoons butter, 2 large yellow onions
- Lower the heat to medium, stir in ¼ teaspoon of the salt, and continue to cook, stirring occasionally, for 30-50 minutes, depending on how dark you'd like your onions. If the fond (the bits stuck to the pan) gets too dark or the onions are browning too quickly, add a splash of water to the pan.
- While the onions are cooking, slice the mushrooms and form the beef into 4 patties.1 ½ lb lean ground beef
- When the onions are golden, remove them from the pan and increase the heat to medium. Add the olive oil and mushrooms and cook, stirring occasionally, for 10 minutes, until they are soft and starting to brown. Season with ¼ teaspoon of salt, add pepper to taste, and remove them from the pan.1 tablespoon olive oil, 8 ounces crimini mushrooms
- Increase the heat to medium-high, add the burger patties, and season them with the remaining ½ teaspoon of salt. Cook until the bottoms have a nice crust, about 3-4 minutes, then flip the burgers and cook until they reach an internal temperature of 165 degrees Fahrenheit, about 3-4 minutes more. Add Swiss cheese during the last 2 minutes of cooking, then remove the burgers from the pan.4 thick slices swiss cheese
- Wipe out the pan with a paper towel. Butter the brioche buns and toast them in the pan, working in batches.4 brioche buns
- Spread mayonnaise (or your favorite burger sauces) on the buns, add a piece of lettuce, and top with a burger, onions, and mushrooms and serve right away.Mayonnaise and butter lettuce
Notes
Nutrition
We have thoroughly tested this recipe for accuracy. However, individual results may vary. See our full recipe disclosure here.
More burger recipes to try next
Check out all of my burger recipes for even more dinner ideas!
