Soak the beans overnight in enough cold water to amply cover them mixed with the bicarbonate of soda.

The next day, drain and place the beans in a measuring jug to get a rough estimate of their volume and transfer to a fireproof earthenware or enamelled cast iron casserole dish with twice their volume of water. Add the unpeeled garlic cloves, sage leaves but no salt and bring slowly to a gentle boil.

Simmer the beans over a very low heat for 2 1/2 hours or until they are tender, removing any scum from the surface at intervals. After just over 1 hour's cooking time, stir in 2 tsp salt and 1 tbsp olive oil.

When the beans are cooked, remove and discard the sage leaves; squeeze the soft puree from the garlic skins into the beans and stir. Add a little salt if necessary.

Trim, prepare and thoroughly wash the escarole; blanch for 2 minutes in a large saucepan of boiling salted water. Drain well and place an equal amount in deep, heated soup bowls; ladle plenty of beans on top and sprinkle a little olive oil and freshly ground white or black pepper over them.