Slice onions into half rings, slice mushrooms. On high heat and fry mushroom and onions, season with salt and pepper until both are golden brown. Remove all ingredients into a bowl.
Mix together, beef and kraft burger seasoning. Form beef patties about ¾ of an in thick.
Place them in same skillet you used for onions, turn heat on low. Cook each side 5 minutes on one side and 4 minutes on the other side.
Place slice of cheese on bottom bun, cooked meat, onion/mushroom mixture, cover top bun with mayo and ketchup, cover the burger with top.
Let it rest for about 3 minutes so the beef wouldn’t be as hot and it will set a little.