Put the Jerusalem artichokes in a medium saucepan, cover with plenty of water and add half the lemon juice. Bring to the boil, reduce the heat and simmer for 10–20 minutes, until tender but not soft. Drain and leave to cool.

Place the Jerusalem artichokes and all the remaining ingredients, excluding the remaining lemon juice and half of the tarragon, in a large mixing bowl and use your hands to mix everything together well. Cover and leave to marinate in the fridge overnight, or for at least 2 hours.

Preheat the oven to 240°C/220°C Fan/Gas Mark 9. Arrange the chicken pieces, skin-side up, in the centre of a roasting tin and spread the remaining ingredients around the chicken. Roast for 30 minutes. Cover the tin with foil and cook for a further 15 minutes. At this point, the chicken should be completely cooked. Remove from the oven and add the reserved tarragon and lemon juice. Stir well, taste and add more salt if needed. Serve at once.