1Mix the mayo, sour cream, horseradish and celery seed in a bowl and set aside.
2In a second bowl mix the parsley and onion.
3Parboil potatoes, peel, cut into 1/8 inch thick slices.
4Place one layer at a time into a large serving bowl.
5After the first layer of potatoes spread a layer of the mayo mix then layer the parsley and onion mix. continue this procedure until the bowl is filled.