Heat ½ tablespoon olive oil in a skillet over medium heat. Finely chop half the mushrooms and add them to the skillet. Cook, stirring, for 4-5 minutes until tender. Season with salt and pepper and remove from the skillet to cool.
In a large bowl, add the ground beef, finely chopped mushrooms from Step 1, 1 tablespoon Worcestershire sauce, dijon mustard, salt, pepper, and garlic. Gently mix the ingredients together and form the meat into 4 patties. Heat a grill or large skillet with ½ tablespoon olive oil on medium high heat and cook the patties 4-5 minutes per side, or until done to your liking. Top each burger with a spoonful of the sliced mushrooms and a slice of swiss cheese and cook another 1 minute until cheese starts to melt. Serve the burgers on a bun with desired toppings.
Recipe by Love Grows Wild at https://lovegrowswild.com/2015/06/mushroom-swiss-burger/