Take an english muffin and split it in two. Spread pizza sauce onto the muffin and sprinkle some garlic salt on it followed by placing the shredded cheese. Place the pepperoni and mushroom with some onion and walla. Place on a foil lined baking tray and cook at 350 degrees until the cheese is getting browned on the edges 15 to 20 minutes. Let them Cool for a few minutes and serve.