I learned how to cook this at a cafe I worked at when I was in high school. It was only served on Sundays. The longer it cooks the more tender the meat becomes. I usually serve this with buttered new potatoes and almond green beans.
Preheat oven at 350. Melt butter in a large frying pan on medium heat.
Sprinkle the minute steaks with season salt on both sides. Dredge in flour. Brown the steaks in the butter, two or three steaks at a time. Be sure not to crowd the pan. When steaks are brown, place them in a 9 x 13 dish.
In the same pan that the steaks were browned in, saute the onion and green peppers until tender. Add the mushrooms. Continue to cook until mushrooms are thoroughly heated.
Mix up the brown gravy mix with one cup of water. Pour the mixture over the contents of the pan. Deglazing the pan..scraping up all the flavorful bits from the bottom of the pan. (***If you do not want to use brown gravy mix, sprinkle the content of the pan with 1/4 cup flour and deglaze with 1 cup of water or beef brother)
Add cream of mushroom soup and one can of water to the pan. Continue to heat the pan and mix the contents until mixture begins to bubble and a fairly even consistency is reached. If the gravy is too thick, add more water as needed...too thin, cook longer.
Pour mixture over steaks in 9 x 13 pan. Cover pan with foil and bake for one hour.