Cod with crispy potatoes and mustard lentils

Main course: serves 4. Total time 40 minutes

Fish, potatoes and pulses are natural partners: think fish, chips and mushy peas. This is a more sophisticated variation.

400g even-sized Belle Fontaine potatoes
4 tablespoons olive oil
4 fillets of cod, about 125g each, with skin
100g Puy lentils
1 carrot
half small onion
1 small stick celery
15g butter
1 shallot, finely chopped
1 tablespoon capers, rinsed and patted dry
2 tablespoons vinaigrette mixed with 1 teaspoon Dijon mustard
1 tablespoon chopped fresh chives
sea salt
freshly ground black pepper

Cook the potatoes in boiling salted water for about 12 minutes until just tender. Drain and cool until you can handle them - they are best peeled hot. Cut into neat dice and toss with 1 tablespoon of the oil. Spread out on a tray, season and let the potatoes absorb the oil as they cool.

Season the skin side of the cod with salt, rubbing it in nicely. Leave for half an hour. This helps to dry out the skin.

Place the lentils in a saucepan with the carrot, onion and celery. Cover with cold water and bring to the boil. Simmer for about 15 minutes or until just cooked. Do not overcook or the lentils will break down. Drain immediately and discard the vegetables. Spread the lentils on a tray to cool. This stops them cooking further.

When ready to cook, beat 1 tablespoon of the oil with the butter in a frying pan, and gently sauté the shallot for about 5 minutes. Scoop out the shallot and reserve. Add another tablespoon of oil to the pan, raise the heat and tip in the diced potato. Cook until nicely golden brown. turning as necessary. Remove, mix with the shallot and capers, and keep warm.

Wipe out the pan and heat the remaining tablespoon of oil in it. When hot, add the fish, skin side down. Cook until the skin crisps up nicely (make sure the heat isn't too high or the skin will burn). I always cook my cod for 90 per cent of the total time on the skin side, then flip over just to brown the other side lightly. Cooking time depends on the thickness of the fillet, but is about 5 minutes in all. Check if the fish is cooked by pressing with the back of a fork. It should be lightly springy.

Reheat the lentils briefly in a saucepan, season and stir in the vinaigrette and chives. Sit a cod fillet on each of four warmed plates, and spoon over the lentils and then the potatoes. Serve hot.