Boil potatoes with garlic, bay leaf, and celery tops to flavor water. Cool, peel and slice.
Mix sour cream, mayonnaise, horseradish, and celery seed.
Mix together onions and parsley.
Place a layer of sliced potatoes in a clear glass bowl or casserole dish. Sprinkle with salt and pepper. Spread a layer of mayonnaise mixture on top of potatoes, followed by a layer of parsley mixture. Repeat layer.