Take your white mushrooms and finely mince them using a knife or food processor. The mushrooms will have quite a bit of moisture in them so feel free to squeeze any excess liquid out with a cloth.
Combine the turkey meat, minced mushrooms, bread crumbs, and seasonings. Mix together until the meat and extras are evenly blended
Form the patties by rolling out a golf ball sized piece of the meat mixture and pressing it between two pieces of parchment paper. Aim for around ¼”-½” patty depth.
Season both sides with salt and pepper before laying them directly on the grill over high heat. Cook for around 3-5 minutes before flipping.
Once the first side is finished cooking, flip the patty over and immediately cover it with a slice of Muenster cheese. Feel free to begin toasting your buns while the burger finishes cooking and the cheese starts to melt.
Remove the patty from the grill and place it on your toasted bun with lettuce, tomato, red onion, ketchup, mustard, and any other burger toppings that you like.