Varenyky are dumplings, when savoury, often filled with potatoes, they are made with unleavened dough
In a large bowl, mix flour and salt.
Add warm water and oil.
Mix, then knead until the dough is smooth and soft (about 8–10 minutes).
Cover and let it rest for 20–30 minutes (important—it makes rolling easier!).
Peel and boil potatoes in salted water until soft.
Drain and mash until smooth.
Finely chop the onion and fry it in butter or oil until golden.
Mix onions into the potatoes, season with salt and pepper. Let cool.
Roll dough thin (about 2 mm).
Cut circles using a glass or cutter.
Place 1–1½ teaspoons of filling in the center.
Fold in half and pinch edges tightly to seal.
Bring a large pot of salted water to a gentle boil.
Add varenyky in batches.
When they float, cook 2–3 more minutes, then remove with a slotted spoon.