• 300 g brown or green lentils, rinsed well
• 1 small onion, sliced
• 1 stick celery, sliced
• 1 bay leaf
• 1.5 litres vegetable stock or water
• freshly ground black pepper
• ½ teaspoon ground cumin
• 1 tablespoon lemon juice
• 1 kg mussels
• snipped chives, to garnish

Put the lentils into a large pan with the onion, celery, bay leaf and stock or water. Season with pepper and cumin, bring slowly to the boil, then cover and simmer until the lentils are soft, about 40 minutes. Remove from the heat and purée until smooth. Add the lemon juice.

While the lentils are cooking, scrub the mussels and remove the beards, discarding any that are broken or gaping open. Put the mussels in a large pan with 80ml of water, cover and steam, shaking the pan from time to time, until the shells open (discard any that don’t). Drain into a colander set over a large bowl. Discard the shells and put the mussels into a bowl. Strain the mussel liquor through a very fine sieve or one lined with damp muslin.

Stir the mussels and liquor into the soup. If the soup is too thick, add a little water. Taste and adjust the seasoning; the mussels should add enough saltiness. Heat through gently, sprinkle over the chives and serve.