Spread the chopped meat on a chopping board in a rectangle. Chop the anchovies very fine. Blend them into the meat with two heavy-bladed knives, using a spreading stroke with one hand and a chopping stroke with the other. Fold the meat in from the edges to the center and then spread it out as before. Add the onion, mustard, and egg yolks and spread and chop. Fold in again from the edges to the center. Spread and chop until it is a rectangle once more. Add the salt and freshly ground pepper. You may add Tabasco and Worcestershire, if you like, but I feel it is not necessary. Spread and chop, this time very well, and again bring in the edges to form a large patty. Turn over, spread and chop again, and re-form a large patty. Place in a bowl and cover with chopped parsley and chives, or form a nice patty and arrange on a board or platter. Garnish with chopped parsley. Serve with rye or pumpernickel breads. Tartar steak may also be shaped into small balls and rolled in chopped parsley or chopped nuts. Serve with toothpicks.