Core apples and chop them into wedges.
Arrange them in a salad bowl and sprinkle with 1 tablespoon of the dressing.
Wash watercress, drain well and pat dry in a tea towel.
Discard coarse stems.
Chop leaves and add to apples, with onion and chives.
Crumble cheese over salad.
Drizzle remaining dressing over top.