Beef Stroganoff

1 tb Vegetable Oil
      1 lb Sirloin Steak, Boneless*
      8 oz Fresh Mushrooms, Sliced
      1 ea Medium Onino, Sliced
      1/4 c  Water
      2 tb Unbleached Flour
      1 ts Dry Mustard
      1 ts Salt
      1/4 ts Pepper
      1 c  Dairy Sour Cream

  *Sliced into thin strips.
 Stir oil and steak in 2-Qt casserole until beef is well coated.  Cover and microwave on high (100%)) until meat is no longer pink, 4 1/2 to 5 Minutes. Remove beef from casserole; reserve meat and juices.
Add mushrooms and onion to meat juices.  Cover and microwave until mushrooms are tender, 5 to 6 minutes.
Shake water and flour in tightly covered jar; stir into mushrooms.
Sprinkle with dry mustard, salt and pepper.  Microwave uncovered to boiling, 30 seconds. Boil until thickened, about a minute.
Stir in the streak strips; add the sour cream.  Microwave uncovered until hot, about 1 minute.
Serve over hot rice or noodles (fettucine).