Step 1Nip out the white fatty gristle of the kidneys using a knife or scissors.
Step 2In a bowl, mix together the flour, cayenne pepper, mustard, salt and pepper.
Step 3Heat a frying pan over high heat until very hot, then add the butter. As the butter melts, roll the kidneys in the spiced flour, then shake them in a sieve to remove the excess flour. Place the kidneys in the sizzling pan and cook for 2 minutes on each side. Add a hearty splash of Worcestershire and chicken stock, and let all of the ingredients get to know each other.
Step 4Remove the kidneys to your two waiting bits of toast, and continue to cook the sauce until it reduces and emulsifies in the pan (do not let it disappear), then pour over the kidneys and toast.