Shortcut Pierogies recipe  2 cups  cooled mashed potatoes  1/2 cup  (1/2 of 8-oz. tub) PHILADELPHIA Chive &amp; Onion Cream Cheese Spread  1/4 tsp.  pepper  36  won ton wrappers  1  egg white, lightly beaten  3 Tbsp.  butter, divided  1/2 cup  BREAKSTONE&#x27;S or KNUDSEN Sour Cream