Mushroom Swiss Burger

These burgers are piled high with Swiss cheese, sauteed mushrooms, and caramelized onions for a super satisfying and flavorful burger!

5 from 2 votes

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Prep Time: 15

Cook Time: 1

Total Time: 1 15

Servings:

Calories: 646kcal

In a large stainless steel skillet, add the butter and the onions. Turn the heat to medium, cover, and cook, stirring regularly, until the onions are softened and starting to brown, about 7-9 minutes.
Uncover, turn the heat to low, and continue to cook, stirring often, until the onions are very soft, sweet, and a deep brown color. If the onion starts to stick at any point, add a splash of water and scrape the bottom of the pan to deglaze. I usually have to do this 3-4 times throughout the process.
You can remove the onions in as little as 30 minutes, or cook them for an hour or longer. They will continue to get softer and sweeter as you go. I take mine out around the 45 minute mark. Season to taste with salt.

Deglaze the onion pan with a splash of balsamic vinegar, broth, or wine--whatever you've got on hand. Melt the butter in the skillet and add the mushrooms.
Let them cook WITHOUT stirring, 4-5 minutes, or until golden brown on one side. Flip and continue to cook until browned on both sides. Add the garlic and saute for about a minute, then season to taste with salt. Remove from heat.

Gently shape the beef into five equal sized balls then use the palm of your hand to press them into a flat patty shape. It’s okay if the edges aren’t perfectly round. Use your thumb to press an indent into the center of each patty, then sprinkle both sides with burger seasoning.
Heat a cast iron skillet over medium high heat. Add the patties and cook until browned on the bottom, about 4-5 minutes. Flip over, and cook an additional 3-4 minutes or until it reaches an internal temperature of 165 degrees. Add the cheese for the last 2 minutes of cooking.
To assemble, spread the mayonnaise on the buns (if using). Top each one with a burger patty, caramelized onions, and mushrooms. Add greens if desired. Serve.

Caramelized onions and mushrooms can be made up to 3 days in advance and stored in the fridge. Reheat before assembling.
Reheat leftover burger patties on the stove top or in the microwave. They'll keep in an airtight container in the fridge for up to 5 days.
If you want to make your burger extra special, toast the buns! Brush the hamburger buns with oil or melted butter and pop them in a skillet over medium heat (you can use the same one you used to cook the onions and mushrooms). They should be perfectly warm and toasty brown in 2-3 minutes.