Spray a frying pan with oil and cook beef over high heat for 3–4 minutes, to your liking. Transfer to a plate to keep warm.
Reduce heat to medium. Add onion, garlic and mushroom. Cook, stirring, for 5 minutes, until soft. Add paprika. Cook, stirring, for 1 minute. Stir in stock, tomato paste and mustard. Return beef to pan. Stir to combine. Bring to the boil, then simmer for 5 minutes, until sauce is thick and beef is cooked through.
Stir in sour cream. Serve beef over pasta and sprinkle with chopped parsley, if desired. Serve with green salad.
Recipe sourced from: Australian Healthy Food Guide