Sift the flour onto the work surface, make a well in the centre. Pour a small amount of hot water and mix it. Knead quite quickly, adding enough water (gradually!) to get the dough soft, but not too sticky.
Divide the dough into four parts. Put three parts away, cover with a clean cloth. Spread the first part of the dough on a floured worktop.
Take the rolling pin and set it on top of the flattened dough. Press down and let the pin rotate as you push it. Roll into a thin piece of dough.
Cut the dough using a round cutter. Portion filling of choice on all the dough circles before folding. Fold dough over filling, press edges together.
Bring a pot of salted water to boil. Reduce the heat to a simmer. Drop pierogi in and cook for 5-6 minutes until they start to float. Remove with a slotted spoon. Serve warm with melted butter.