Soak the beans overnight in plenty of cold water. Drain and dry.

In a heavy bottomed pan put the beans together with the onion, bay leaf, garlic head, peppercorns and half the oil. Add enough cold water to cover and bring to boil.
Simmer gently for 1-1½ hours, or until the beans are tender.

Heat the remaining oil in a frying pan and stir in the p and fry for a few seconds. Then add the sherry vinegar and mint stirring slowly.
Taste for salt and add some if necessary.

Allow to rest for half an hour for the flavours to combine.
Serve hot