In a large, non stick frying pan, melt half the butter with half the oil. Increase the heat, then quickly sear the beef until browned on both sides. Remove the meat and set aside. Repeat with the mushrooms then set aside with the beef
Put the pasta on to boil
Add the remaining butter and oil to the pan and soften the shallots for a few minutes. Stir in the flour then gradually stir in the stock. Simmer for 5 minutes until thickened, and then stir in the mustard, puree, creme fraiche and seasoning. Simmer for one more minute then return the beef and mushrooms to the pan
Drain the pasta, toss with half the parsley, season then serve with the stroganoff. Sprinkle with the remaining parsley
