Put yogurt, salt, pepper powder and chopped parsley in a bowl and mix well.Put yogurt mixture in a piping bag fitted with nozzle and chill in the refrigerator.
Pass cookie cutter through beetroots to get cylinders. Slice beetroot into thick discs.Place 5-6 discs on a platter in a single layer. Pipe out portions of chilled yogurt mixture at centre of discs.
Put another disc on top of each to make a sandwich. Pipe out portions of yogurt mixture at centre one more time. Garnish with chopped pistachios and parsley sprigs. Serve.