Cook potatoes and grate into a bowl. Add the grated onion and beaten eggs. Add salt, seasoned with mint and mix. Sift the flour into a deep bowl and add salt. With stirring, pouring water. The dough is mixed, so that it remains moist. Rested briefly. Rested dough is divided into two. On the one part on a floured top roll cover with a diameter larger than the diameter of the tray (28 cm). 1/3 of the butter melts in the tray. Is placed inside the finished crust to cover the walls and hung from the side. The filling is spread over crust. Closes with second crust Roll and sealed, the dough hanging along the walls of the tray is rolled inward. Top distributed the second third of the butter. Bake for about 20 minutes at 180 C in a preheated oven. Then turns using a large plate, goes back into greased with the last part of the butter tray. Bake the other side for about 20 minutes.