Pierogi

Steps

1. 1
   Mix the flour, warm water, egg and salt into a soft dough and knead 8 minutes until smooth and elastic.
2. 2
   Rest it covered for 30 minutes — unrested dough springs back and will not roll thin.
3. 3
   Fry one diced onion in butter until golden and mix it with the mashed potato and curd cheese. Season hard; the filling must taste slightly over-seasoned.
4. 4
   Roll the dough out to 2 mm and cut 8 cm rounds.
5. 5
   Put a spoon of filling on each, fold into a half-moon and pinch the edge firmly, pressing out any air.
6. 6
   Boil in batches in well-salted water. They are ready about 2 minutes after they float.
7. 7
   Fry the remaining onions in the rest of the butter until deep gold.
8. 8
   Toss the drained pierogi in the onion butter and serve with soured cream.