* 50 g (2 oz) butter
* 1 onion, peeled and chopped
* 450 g (1 lb) calves liver, washed, rinsed, trimmed and sliced as thinly as you can
* 3 tablespoons chopped parsley
* 3 tablespoons chopped sage
* Sea salt and freshly ground black pepper
* 30 ml (2 tablespoons) sherry vinegar - red wine vinegar will do , but it's worth getting sherry vinegar anyway, you won't regret it!

===Method===
* Fry the onions in the butter until soft, about 4 minutes
* Add the liver, sage and half of the parsley and season to taste with salt and pepper
* Fry until browned and tender, but don't overcook it or it will be as tough as old boots. (It's quite ok to eat liver rare)
* Reserve the liver and onions and keep warm
* Deglaze the pan with the sherry vinegar by bringing it to the boil whilst stirring. Reduce the heat and simmer for a minute
* Pour the hot sherry over the liver and sprinkle with the remaining parsley

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