1In a large bowl, stir together the flour, baking powder and salt. In a small bowl (or Pyrex measuring cup) stir together the butter, milk and egg; add to the flour mixture and stir until you have a dry, shaggy mixture. Add the water about a third at a time, until you have a soft, slightly sticky dough. Knead it about 10 times, then cover with a towel or plastic wrap and let rest on the countertop for 20 minutes.
2To make the filling, stir together the sugar and flour; stir in the blueberries. On lightly floured surface, roll out the dough to a scant 1/4-inch thickness. Using a 3-inch round cutter, cut into rounds. Stretch each round slightly; fill with a spoonful of the blueberry mixture, ensuring you get some of the sugar-flour in there as well.
3Pull dough over filling into semicircle; pinch edges together to seal. Cover with tea towel. Repeat with remaining dough and filling. Freeze in a single layer or cook immediately.
4In large pot of lightly salted water, boil perogies in batches, until they float to the top and the dough is tender, about 10 minutes. With slotted spoon, transfer to dish; drizzle with butter to prevent sticking. If you like, brown the well-drained boiled perogies in a hot pan with butter until crisp and golden; dribble the remaining butter from the pan overtop. Serve with sour cream or whipped cream. Makes about 3 dozen peroghies.