You can really use any cut of beef for this as long as it is a tender cut like sirloin or beef tenderloin, beef tenderloin is expensive, so I most always use a sirloin roast sliced very thin or a thick beef rib steak sliced thinly. Place the beef in the freezer to partially freeze, it will make slicing easier. To save time prepare the sour cream/paprika sauce a day ahead and refrigerate. This is a delicious beef recipe that can be doubled if desired. Cooking time is for the sour cream sauce and for browning the beef slices.