Cut the steak into strips. Then mix 1tbsp of the oil and the stock cube into a paste and toss in the beef strips.

Heat the 2tbsp of oil in a frying pan, add the paprika and onion and cook slowly until soft.

Add the mushrooms and fry gently for 3 minutes then transfer to a hot plate.

In the same pan, fry the beef quickly for just a minute and return the onion mixture to the pan, then pour in the sour cream.

Bring to the boil and simmer for a minute until thickened. Stir in the lemon juice before serving.