- Boil the potatoes: Cook the potatoes in a pan of boiling water for 10 minutes or until tender. Drain. Meanwhile, prepare a large pan of boiling water with a large steamer on top. Cut four pieces of foil, each large enough to enclose a folded fish fillet.
- Prepare the vegetables: Arrange the leeks in the steamer with the carrots, in one layer if possible, then set aside. Grate the zest from the lime, or use a zester, and set aside in a small bowl. Cut the lime into quarters.
- Make the fish parcels: Lay a fish fillet skin side down on each piece of foil. Top the wide end of each fillet with 3 cucumber slices and a bay leaf. Season to taste. Lightly squeeze a little juice from a lime quarter over each fillet and fold the narrow end over. Top with the squeezed lime quarters. Drizzle 2 tsp olive oil over each. Bring the foil up to enclose the fillets in neat parcels that will fit inside the steamer. Set the parcels aside.
- Steam the vegetables: Cook the prepared vegetables in the steamer for 5 minutes. Put the courgettes on top of the part-cooked vegetables, cut sides up. Add the foil parcels and steam for a further 10 minutes or until all the vegetables are tender and the fish is cooked.
- Add the flavourings: Open the foil parcels and sprinkle a little lime zest and shredded sorrel into each. Divide the vegetables among four plates. Transfer the fish to the plates using a fish slice or spatula, then pour the juices from the foil over. Serve immediately.
*For red mullet, use sea bass, plaice or lemon sole fillets. *For sorrel, use parsley, or a mixture of parsley, dill and a little tarragon. Alternatively, for a stronger flavour use rocket or watercress.
Chinese-style sea bass: Follow the basic recipe but use sea bass fillets instead of red mullet and omit the lime. Add 1 shredded spring onion and 1 tsp grated fresh root ginger to each fillet instead of the cucumber and bay. Sprinkle them with 1 tsp each of toasted sesame oil, dry sherry and light soy sauce mixed together, instead of the olive oil. Steam 200g baby corn, baby carrots and mange-touts and 200g asparagus stalks (woody ends removed) as step 4, instead of the carrots and leeks. Add 200g halved pak choi in place of the courgettes 4 minutes before the end of the cooking time. Omit the sorrel and sprinkle with a little chopped fresh coriander, if you like. Serve with plain cooked rice.