Method
Melt 25g butter in a large frying pan and cook the onion until soft.
Add the mushrooms and cook over a high heat until golden. Remove from the pan and reserve.
Melt 25g butter over a high heat and cook the steak, in batches, stirring, for about 3-4 minutes until well browned. Be sure the fat in the pan is hot again before adding the next batch.
When all the meat is cooked, return it to the pan, add the onion, mushrooms and crème fraiche and warm gently.
Serve the beef on top of the cooked tagliatelle and top with chopped parsley.
