Skin and core the kidneys with a pair of scissors.
In a bowl mix together the flour, cayenne pepper and mustard powder. Toss the kidneys in the flour and shake off the excess.
Preheat a frying pan; add 2tsp of the oil and the butter, fry the kidneys for 3-4 minutes until golden. Remove from the pan and set aside.
Add the remaining oil to the pan with the shallots, garlic and mushrooms and sauté over a medium heat for 2-3 minutes. Add a few drops of Worcestershire sauce to the pan, pour in the stock and reduce by half. Add the crème fraîche and kidneys to reheat for 1 minute and season to taste.
Finally, add the chopped parsley an extra sprinkling of cayenne pepper and serve on hot toast.
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.