Through the feed opening of a running blender add, 1 at a time, the vinegar, shallot, chives, salt and pepper. Leaving the blender running, add the oil in a slow thin stream and allow to emulsify. Taste and adjust seasoning, as needed, with salt and pepper.
Toss together celery, apples, walnuts and onions, and with enough dressing to coat.
2007, Robert Irvine, All Rights Reserved.