First step is to caramelize the onions. This takes a little time, but it's well worth it. Spray a large skillet with cooking spray and place all onions in the skillet. Turn heat to low/ medium setting. Just hot enough to brown the onions a little, but do not let them get blackened. You can add a little salt as you stir, but just a pinch. Add tbsp. of water if they start to get too dry. Keep stirring the onions every 10 minutes until they are golden brown and sweet tasting. Add the mushrooms to the onions and cook until the mushrooms are cooked through and about half the size they were. Add the Golden Mushroom Soup at this point and let the mixture simmer while you prepare the burgers.
To prepare the burgers you will first separate the meat into 4 parts. Then split the parts in half. Use one half to form the bottom part of the patty. Then on top of the bottom half... lay a slice of Swiss cheese that has been cut a little to strips so that you can add it to just the middle. Then lay the other half of the beef on top of that and form the patty with the Swiss cheese inside. Form all patties this way. Cook on medium high heat until the inside temp reaches the safe point for ground beef.
You can also toast the buns and use melted butter and garlic on top... optional but very tasty!
Once the meat is finished cooking then layer on the meat and then the onion and mushroom sauce to the top. I let the sauce drip off the sides because it's so good! Then it's ready to enjoy!