Ingredients

Instructions

1. 1

   In a large bowl, gently combine the ground beef, soy sauce, Worcestershire sauce, and Dijon mustard. Be careful not to overmix. Form into 4 patties.

2. 2

   Heat olive oil in a large skillet over medium heat. Add sliced onions and cook until softened and caramelized, about 8-10 minutes. Remove from skillet and set aside.

3. 3

   Add shiitake mushrooms and minced garlic to the same skillet and sauté until tender and browned, about 5-7 minutes. Season with salt and pepper.

4. 4

   Season the burger patties with salt and pepper.

5. 5

   Increase heat to medium-high. Cook the burger patties for 4-5 minutes per side for medium doneness, or to your desired level of doneness. During the last minute of cooking, place a slice of Gruyere cheese on each patty and allow it to melt.

6. 6

   Toast the burger buns lightly.

7. 7

   Assemble the burgers: Spread the caramelized onions on the bottom bun, top with the cheese-covered patty, then the sautéed shiitake mushrooms. Place the top bun and serve immediately.