My mom calls this "salatka swiateczna" ("Holy Salad"). It uses leftovers from Easter (eggs, horsedarish, sour cream, etc.) and tastes amazing; very fresh and crisp! It has a strong, bold flavor and is very good with a meat dinner like pot roast or steak.
If you are using horseradish from a jar, let it sit in a strainer to get out the excess water. If you are using fresh horseradish, wash and peel it, and grate it.
Peel celery root and wash it very well. Pat it dry and then shred it into medium strips using the medium-size side of a vegetable shredder.
Wash and shred radishes into the same bowl as the celery root.
Peel eggs and mash them in a bowl using a fork. Add to radishes and celery root.
Add in the mayo, sour cream, horseradish, chives, salt and pepper. Mix, but not too vigorously so the ingredients don't all mash together. Taste it and adjust salt and pepper levels. This is a very good side salad to have with a heavy meat dish. Enjoy!