While piping hot add 1/2 lb grated cheddar cheese.
Cool and fill squares.
Combine 1/2 lb dry cottage cheese with all moisture squeezed out 1 beaten egg. (2 tbsp sugar and vanilla optional.)
Drain 2 cups sauerkraut and chop coarsely. Brown in oil and season to taste.
Mix flour, eggs, salt and butter to make dough. (If dough is too soft, the seems will not stick.) Knead until smooth. Divide into 2 portions. Roll out 1 portion, and cut into 2-inch squares. Place small ice-cream scoop of filling on each square. Fold in half to make a triangle. Pinch edges closed. Follow same methods for remaining dough. Drop in simmering water and cook until pirohi come to top. Continue cooking until tender.
Saute butter and onions in pan. Smother cooked pirohi with butter and onions before serving.