Place potatoes in a bowl and wash under cold, running water until water runs clear. Place in a medium saucepan with salt. Add enough water to generously cover. Bring to a boil, reduce to a simmer, and cook, uncovered, until soft, about 15 minutes. While potatoes are still warm, mash with a fork, in a food mill, or gently in a food processor.
In a medium saucepan, warm sour cream and butter. Fold warm sour cream mixture into potatoes, add salt and pepper to taste. Serve immediately. Garnish with cracked pepper.
In a small bowl stir all the ingredients together. Spoon over vegetables or drizzle lightly over dressed salads as a garnish.