Pierogi Ruskie (Polish Dumplings)

Step 1: Put the potatoes and 1 tbsp salt in a large saucepan. Add cold tap water until it is about 3 cm / 1 inch above the potatoes. Bring to a boil over high heat, then reduce the heat to medium-high and simmer for 15 minutes, or until the potatoes are soft.

Step 2: Drain the potatoes, then pass them through a potato ricer into a bowl, or mash them with a potato masher.

Step 3: Immediately add the butter, cheese, salt and pepper. Mix with a wooden spoon until fully combined.

Step 4: Spread the filling about 1 cm / 1/2 inch thick on a tray. Cover it with cling wrap, pressing the wrap into full contact with the filling. Cool on the counter for about 30 minutes, then refrigerate until cold, at least 1 hour.

Step 5: Heat the water and butter in a small saucepan over medium heat just until the butter melts; do not boil the water. You can also do this in the microwave. Turn off the heat.

Step 6: Whisk the flour and salt in a mixing bowl. Make a well in the centre, add the butter water and egg, and mix until a shaggy dough forms.

Step 7: Scrape the dough onto a lightly floured work surface. Knead for 5 minutes, until smooth. A stand mixer can also be used.

Step 8: Wrap the dough with cling wrap and leave it on the counter for 30 minutes.

Step 9: On a lightly floured surface, roll the dough to 3 mm / 1/8 inch thick. Cut out rounds with a 7.5 cm / 3 inch cutter. Cut as many as you can, then gather the surplus dough into a ball, wrap it with cling wrap and set it aside for later.

Step 10: Place 1 tablespoon of filling in the middle of a dough round. Dip a finger in water and run it along the edge of half the circle. Fold the dough over the filling and press to seal, making slight indents without pleats.

Step 11: Place the pierogi on a lightly floured tray. Continue wrapping the remaining pierogi, rolling out the remaining dough as needed. The batch should make about 30.

Step 12: In a nonstick skillet, melt the butter over medium heat until foamy. Add the onion and salt and cook, stirring regularly, for 10–15 minutes, until golden at the edges. Scrape the onion butter into a bowl and set aside; it can cool.

Step 13: Cook the pierogi in batches of 10–12 at most so they have room in the water and can be tossed in the butter. The directions that follow are for cooking and serving 10.

Step 14: Bring about 3 litres / quarts of water to a boil with 1 tbsp salt. Lower 10 pierogi into the water and cook for 5 minutes, until they float to the surface.

Step 15: Dip a jug into the cooking water and scoop out about 1 cup. Use a slotted spoon to transfer the pierogi to a bowl, or drain them if you are not cooking more batches.

Step 16: Melt the butter in a large skillet over medium heat. Add one-third of the onion butter, the cooked pierogi and 2 tablespoons of the reserved cooking water. Toss on the heat for 1 minute, until the pierogi are coated in butter.

Step 17: Slide the pierogi onto a serving plate, scraping out the butter. Sprinkle with parsley and add a dollop of sour cream.