Place on jellyroll pan or cookie sheet. Season with salt, pepper and onion salt. Place in 200-degree oven for 45 minutes. Cooking too long will cause finger steaks to become too dry. These may also be made up ahead of time, frozen on a cookie sheet, then deep fried.
Place steaks on grill over medium heat.
Grill steaks, uncovered to the doneness you prefer. Season steaks with salt, as desired. Layer raw steak on the bottom. Sprinkle 1 package dry onion soup mix over steak. Top with mushrooms.