Filling: Combine the pork, pâté, onion, potato starch and season with salt, sugar and pepper. Mix thoroughly until all of the ingredients are uniformly amalgamated. To ensure that the mixture is properly seasoned, add the salt gradually and taste after each addition by cooking a spoonful in the microwave (but without the spoon).
Preheat oven to 175°C.
Work with one pastry sheet at time, leaving the other one in the fridge until ready to use. Unfold the puff pastry sheet onto a lightly floured surface. Cut out 6-8 cm diameter circles using a round cookie cutter or drinking cup. Combine the remaining pieces of puff pastry dough, roll it out and cut additional circles.
Place about a tablespoon of filling onto the center of a puff pastry circle, and top with another circle. Seal by pressing the sides down with a fork. Place the meat pies onto a flat-edged baking sheet lined with parchment paper. Brush the surfaces with the beaten egg. Bake for about 25 minutes. Be sure to watch them during the last few minutes of baking to ensure they have sufficiently browned but are not burnt. Transfer them onto a rack to cool once removed from the oven.