Place the vinegar, mustard, honey, shallots, and pepper in a blender container. Process on high speed until well mixed. With the blender running, slowly pour in the oil to form an emulsion. Trim and wash the celeriac. Cut into a fine julienne and place in a lg bowl. Add the lemon juice and combine well to keep the celeriac from discoloring. Mix in the apples, yogurt, onions, and dressing. Serve on a bed of spinach with the radishes. The Healing Foods Cookbook