1. Mix apples, yogurt, cheese, salt and mustard together. Chill for an hour.
2. On a flat serving dish arrange lettuce leaves in a circle.
3. Pile the apple mixture on the lettuce leaves. Surround with evenly placed cucumber slices.
4 Chill for another hour before serving.
5. This delicious and unusual salad goes excellently with roast meat and thinly sliced brown bread.