In a large saucepan cover the potato pieces with cold salted waterand set over medium heat. Bring to a boil, then lower the heatslightly and cook uncovered, stirring a few times, until the potatoesare just tender, about 12 minutes. Drain and transfer to a largebowl. Pour the pickle juice over the hot potatoes, stir gently andcool to room temperature.
Place the diced red onion in a small bowl and cover with ice water.
Let sit 20 minutes to reduce the acidity. Drain and squeeze out theexcess moisture with a paper towel. Add to the potatoes.
In a medium bowl stir together the mayonnaise, sour cream,horseradish mustard, salt, pepper, pickles and chives. Pour thismixture over the potatoes and toss gently. Add the eggs and tossagain. Spoon into a serving container. The salad can be prepared upto 1 day ahead. Refrigerate, covered.
Sprinkle salad with paprika at serving time.