Method

Season beef strips with salt, pepper and dust lightly with flour. Heat oil in a wide pan over very high heat until almost smoking. Sear beef in batches for 1–2 minutes total — you want a crust, not grey boiled beef. The beef should be pink inside. Remove and rest on a plate.
About 5 min
Reduce heat to medium. Add butter to the same pan. Sauté onion for 6 minutes until softened. Add garlic and cook 1 minute. Add mushrooms, increase heat and cook for 6–8 minutes, stirring occasionally, until mushrooms are golden and all moisture has evaporated.
About 11 min
Add Worcestershire sauce and Dijon mustard. Stir 1 minute. Pour in beef stock. Bring to a simmer and cook 3 minutes to reduce slightly.
About 11 min
Reduce heat to very low. Stir in sour cream gradually, don't let it boil after adding it or it will curdle. Heat gently 2 minutes until warmed through.
About 11 min
Return the rested beef (and any juices) to the sauce. Stir gently and warm through for 1 minute — do not overcook the beef. Taste and adjust salt and pepper.
About 11 min
Serve immediately over egg noodles or steamed rice. Garnish generously with chopped parsley.
About 3 min

Nutrition per serving (estimate)

Contains: gluten, dairy, eggs