Ingredients
For the Burgers
- 1½ lbs. 85% lean ground beef (80% or 90% lean can be used if preferred)
- 1 tsp kosher salt
- ½ tsp ground black pepper
- 1 tsp minced fresh rosemary (optional, or substitute with thyme)
For the Mushrooms
- 3 tbsp unsalted butter
- 1 yellow onion, sliced
- 8 oz. sliced mushrooms (about 1 standard package, any variety)
- 1 tbsp balsamic vinegar
- Salt and pepper, to taste
For Assembly
- 6 brioche hamburger buns
- 6 tbsp unsalted butter (¾ stick)
- 6 slices Swiss cheese
- Mayonnaise (optional, for topping)
- A few handfuls of arugula (optional, for topping)
Instructions
- Prepare the burger patties: In a large bowl, gently mix the ground beef, kosher salt, black pepper, and fresh minced rosemary until just combined. Divide the mixture evenly into 6 patties and set them aside.
- Cook the mushrooms and onions: Heat 3 tablespoons of unsalted butter in a cast iron skillet over medium-high heat. Add sliced yellow onions and cook, stirring occasionally, until softened and golden brown, about 10 to 12 minutes. Add the sliced mushrooms to the skillet and continue cooking until they become caramelized, about 10 minutes more.
- Deglaze and season mushrooms: Stir in 1 tablespoon of balsamic vinegar along with 2 tablespoons of water to scrape up the browned bits from the skillet’s bottom. Season with salt and pepper to taste. Remove the mushroom mixture from the heat and set aside.
- Toast the brioche buns: Wipe out the skillet and return it to medium-high heat. Spread ½ tablespoon of butter on both the top and bottom halves of each brioche bun. Place the buns butter-side down into the hot skillet and toast until golden and crisp, about 3 to 5 minutes. Remove and set aside.
- Cook the burger patties: Place the prepared beef patties into the skillet over medium-high heat. Cook until a dark brown crust forms on the bottom side, then flip each patty and cover with a slice of Swiss cheese. Cover the skillet and cook for 5 to 6 minutes or until the cheese has melted and the patties are cooked through.
- Assemble the burgers: If desired, brush the bottom halves of the toasted buns with mayonnaise. Layer on the cooked burger patty topped with melted Swiss cheese, then spoon over the caramelized mushroom and onion mixture. Add a handful of fresh arugula if you like, and finish with the top bun. Serve immediately and enjoy!
Notes
- Using 85% lean ground beef ensures juicy burgers, but you can adjust the fat content to your preference (80% for juicier, 90% for leaner).
- Fresh rosemary adds a lovely earthy flavor, but thyme works well as a substitute.
- Be patient caramelizing the onions and mushrooms for maximum flavor depth.
- Toasting the buns in butter adds a deliciously crispy texture and richness.
- Mayonnaise and arugula toppings are optional but add creaminess and a fresh peppery bite, respectively.
- Use a cast iron skillet for even heat distribution and great searing results.
- Prep Time: 5 minutes
- Cook Time: 35 minutes
- Category: Entree
- Method: Stovetop
- Cuisine: American
