Rossolye (Estonian vinaigrette with herring and beets)

http://cookbook.rin.ru/cookbook_e/recipes/29747274.html

Ingredients:

Dressing:
3 teaspoons of powdered mustard
1 1/4 teaspoons of sugar
1 to 2 tablespoons of warm water
1 cup of sour cream

Salad:
2 hard-boiled eggs, finely chopped
2 large or 4 small boiled and peeled fresh beets, or canned beets, cut into 1/4-inch dice
1 pound (about 3 medium) boiled potatoes, peeled and cut into 1/4-inch dice
2 pound (about 2) sour dill pickles, cut lengthwise into narrow strips, then crosswise into 1/4-inch-wide bits
3 fillet of pickled herring, drained and cut into 1/4-inch dice.
4 pound of boiled beef, or cooked ham, veal or lamb, trimmed of fat and cut into 1/2-inch dice
5 large, tart red apple, cored, peeled and cut into 1/4-inxh dice
3 hard-cooked eggs, cut into quarters

Directions:

1. In a large mixing bowl, combine the finely chopped eggs, diced beets, potatoes, herring, meat and apple. Add sour cream dressing and toss together lightly but thoroughly until all ingredients are well moistened with the dressing.
2. Traditionally, rossolye is mounted high on a square or round serving plate, garnished with sliced hard-cooked eggs, and chilled.
3. Dressing: In a small bowl, combine the dry mustard with 1/4 teaspoon of sugar and stir in 1 to 2 tablespoons of warm water, or enough to make a thick paste. Set aside for 15 minutes. Then stir in the sour cream and the remaining teaspoon of sugar.