I stumbled onto this one when I had a small piece of loin and didn't want anything to tough to cook. I took a small onion, diced it, a couple tablespoons of butter or margarine, melt the butter and saute onions until clear. Add a large handful of fresh sliced mushrooms, cook for a couple minutes, cut your loin into 1" chunks, add to the pan, salt and pepper to taste, a sliced clove of garlic makes it excellent if you like garlic. About the time the meat is a good medium to medium rare, at a dash of red wine and cook it until it is reduced down to a thick sauce, toss the meat and shrooms in it until coated and enjoy, it takes about 15 minutes total, start to eat.
Yardbird

lion?