Creamy Cube Steak & Potato Casserole with Onion & Mushrooms

Creamy comfort food from the 70's!  I think this old favorite was  a state fair prize winner.     If you avoid beef cube steaks because you think they're  tough, try this  tasty  dish,  layered with potatoes, onions and mushrooms in a rich buttermilk* sauce.  Even my kids ate the  onions and mushrooms, which was unusual.  The buttermilk tenderizes the steaks, but if you're  still  ultra-paranoid about  cubed steak tenderness, sprinkle them with a little Adolph's tenderizer  before browning them. 

Brown 4 cube steaks in 4 TB oil. Remove from pan. Saute 2 medium onions, sliced, and 1 lb sliced fresh mushrooms in the same pan, then drain them on paper towels.

Combine 1 can cream of mushroom soup with 2/3 c. buttermilk*, 1 tsp salt, 1/2 tsp pepper.

In a greased or sprayed 2-1/2 qt baking dish, make 2 layers. Alternate  4 medium potatoes,  peeled & sliced, ( actually, that's up to you -- I don't  bother to peel  them)   with the steaks and the onion-mushroom mixture  and the sauce. Bake uncovered at 350 for one hour.  Start loving tender  cube steaks again !

* I seldom have buttermilk around...  sour milk is always a good replacement for that tangy taste :   2/3 c milk that you've added 1 scant TB vinegar to.  Let it sit  minutes  to thicken.