Pierogi

Dough: 300 g all-purpose flour; 1 egg; 130 ml warm water; plus the remaining ingredients listed for this component. Knead dough ingredients until smooth; rest covered 30 minutes. Add the liquid gradually, knead until smooth and cover so the surface does not dry. The dough should relax enough to roll without springing back.

Filling: 400 g cooked peeled potatoes, cooled; 250 g dry farmer cheese (twaróg); 1 onion (120 g), minced; plus the remaining ingredients listed for this component. Cook onion in filling butter until golden. Mash potatoes, crumble cheese and mix with onion, filling salt and pepper; cool. Use medium-low heat and stir onion until golden, not burned. Mash the potatoes smooth, crumble the cheese finely and mix until there are no pockets of seasoning. Spread the filling in a shallow dish and cool promptly.

Roll dough 2 mm thick, cut 8 cm circles and enclose about 1 tbsp filling in each sealed crescent. Keep unused dough and circles covered. Leave the border free of filling, squeeze out air and pinch the whole seam firmly. Set pieces on a lightly dusted tray without touching.

Serve: 25 g butter; 150 g sour cream. Boil in batches until floating, then 2-3 minutes more until skins are tender. Drain and toss with serving butter; serve with sour cream. Use a roomy pot and add pieces separately. Floating begins the final cooking time; cut one to check a tender wrapper without a raw flour line. Lift with a slotted spoon, drain well and toss gently so the seams do not tear.