Into the bowl of a stand mixer, add the egg, sour cream, butter and salt into bowl of stand mixer and mix together.  

Add the flour and knead with the dough hook for 6-8 minutes until a soft supple dough has formed.

To make the dough by hand, add the egg, sour cream, butter and salt into a small bowl and whisk together to form a batter then pour the flour onto a clean work bench and make a well in the centre.

Add the sour cream mixture and mix thoroughly with your hands until the ingredients are incorporated together and a smooth dough has formed.

If the dough feels a bit too sticky while kneading due to variations in egg size or sour cream thickness, just dust in an extra tablespoon of flour at a time until it's smooth and elastic.

Wrap the dough in plastic wrap and refrigerate for 2 hours to chill.

Prepare the filling of choice, and refrigerate until use.

When the dough has chilled, roll to 1/8" thickness and use a round cookie cutter to cut 3" rounds.

Place 1 tbsp of filling into the centre of each round, fold over into a half moon and press the seam closed.

Crimp or scollap the edges if desired.

To cook the pierogies, bring a pot of salted water to a rolling boil, add the pierogies and after 3-4 minutes, when they are floating, remove and set aside to drain.

Alternatively, steam the pierogies in a steamer basket over a pot of simmering water.

For crisy pierogies, after boiling or steaming, heat a skillet over medium high heat with a tablespoon of olive oil.

Place the pierogies into the skillet, add a tablespoon of water so it sizzles, cover immediately and fry for 3 minutes.

Flip and repeat.

Serve with choice of garnish.