Place the beans in a flameproof casserole dish with sufficient water to completely cover them and the unpeeled piece of ginger. Bring to the boil and then simmer for 2 1/2 hours, partially covered to allow the steam to escape. The beans should be very tender. Add salt when they are nearly done. Drain, reserving about 8 fl oz (225 ml) of the cooking water.

Discard the ginger. Put them through the vegetable mill with a fine-gauge disc fitted and return the puree to the casserole dish; stir in some or all of the reserved liquid so that the puree is thick but not stiff. Set aside, ready for reheating.

Make the sauce: slice the peeled garlic cloves and blanch for 3 seconds in a small saucepan containing some boiling salted water; drain at once and rinse in a sieve under running cold water to refresh. Blot dry with a piece of kitchen paper.

Heat the oil in a heavy-bottomed saucepan and fry the garlic slices very gently over a low heat until they are a very pale golden brown. Increase the heat slightly and add the diced flesh from the skinned, seeded tomatoes; cook for 1 minute while stirring gently. Add a pinch of salt and remove from the heat; stir in the pili-pili relish and keep warm.

Heat the bean puree over a low heat, stirring continuously until it comes to the boil. Season. Spoon the tomato mixture into the middle of each bowl of bean puree, distributing an even number of garlic slices on each serving. Sprinkle with the chopped coriander and serve with hot pitta bread and rocket salad.