1.Bring A Large Pot Of Salted Water To A Boil. Add Potatoes And Cook Until Tender But Still Firm, About 15 Minutes. Drain, And Mash With 1 Tablespoon Butter And Black Pepper. Stir In Sour Cream, Horseradish And Parsley. Whip Potatoes And Place In Medium Serving Bowl. 2.Melt Remaining 1 Tablespoon Butter And Pour Over Potatoes. Serve Immediately.