Put the beans into a pan and add cold water to cover by 2.5 cm (1 in).

Add half the onion, half the garlic, the bay leaf and the chilli(es). Bring to the boil and boil vigorously for about 10 minutes. Put the beans and liquid into an earthenware pot or large saucepan, cover and cook over a low heat for 30 minutes. Add boiling water if the mixture starts to become dry.

When the beans begin to wrinkle, add 15 ml (1 tbsp) of the corn oil and cook for a further 30 minutes or until the beans are tender. Add salt to taste and cook for 30 minutes more, but do not add any more water.

Remove the beans from the heat.

Heat the remaining oil in a small frying pan and saute the remaining onion and garlic until the onion is soft. Add the tomatoes and cook for a few minutes more.

Spoon 45 ml (3 tbsp) of the beans out of the pot or pan and add them to the tomato mixture. Mash to a paste. Stir this into the beans to thicken the liquid. Cook for just long enough to heat through, if necessary. Serve the beans in small bowls and garnish with sprigs of fresh bay leaves.