Swiss Steak Quickie
["2 Tbsp. butter or margarine", "1 pkg. dehydrated onion soup mix", "1 1/2 lb. boneless chuck roast, cut 1-inch thick", "1/2 lb. fresh mushrooms, sliced *"]
["*May use 1 can mushroom soup, undiluted."]
["butter", "onion soup", "chuck roast", "fresh mushrooms"]