Rinse kidneys under cold running water and pat dry
Using scissors cut the core out of the kidneys, cut into pieces
Put flour salt and pepper into plastic bag add kidneys and toss to coat
Peel and finely dice onion
Heat oil and gently fry onions until soft
Shake excess flour from kidneys and add to pan
Cook for 3-5 mins
Add tomato puree, mustard to frying pan
Gradually add 300 ml water, stirring constantly
Add Worcestershire sauce
Reduce heat, cover and simmer for 15-25 mins, stir occasionally
Serve on hot buttered toast sprinkled with parsley