Cover potatoes with stock and enough water to cover the potatoes by 1-inch. Bring to a boil and cook potatoes 12 to 15 minutes until tender. Drain potatoes and place back in hot pot.
Combine the scallions, celery, vinegar, sugar, horseradish and olive oil in a small bowl. Pour over the hot potatoes to absorb.
Season the salad with celery seed, dill, salt and pepper.