Combine 2 tablespoons each mayonnaise, sour cream and chopped chives, 1 tablespoon each apple cider vinegar and chopped dill, 1 teaspoon dijon mustard and a pinch of sugar in a large bowl. Boil one 13-ounce package frozen mini potato pierogi as the label directs, adding 1 cup frozen peas. Drain and rinse under cold water; pat dry and add to the dressing. Season with salt and pepper; toss. Chill.