Waldorf Salad

Toast the walnuts in a dry frying pan over medium heat for 4 minutes, shaking often, until they smell nutty.

Tip them onto a plate to cool, then break them roughly in half.

Quarter and core the apples and cut them into 1cm dice, leaving the skin on.

Toss the apple with the lemon juice immediately, before anything else is prepared.

Cut the celery into pieces about the same size as the apple.

Stir the mayonnaise, yogurt, mustard, salt and pepper together in a large bowl.

Fold in the apple with all its lemon juice, the celery and most of the walnuts.

Chill for 30 minutes.

Arrange the lettuce leaves on a plate and spoon the salad into them.

Scatter the remaining walnuts and the chives over and serve cold.