Put the flour on a board and make alittle well in it. Put 1 whole egg and 1 egg yolk in the well. (Set the egg white aside to use in Step 3.) Add ¼cup water and ½teaspoon salt. Knead the mixture into a hard dough. If too dry, add alittle more water. Knead until the dough is smooth and shiny. Let it rest for 15 minutes.
Sprinkle the board with flour and stretch the dough to a heavy noodle thickness, about ⅛inch, and cut it into 3-inch squares.
In the center of each square put ½tablespoon of jam. Brush the edges of the squares with lightly beaten egg white. Now fold each square cater-cornered, making a triangle. Pinch the edges together to seal completely so jam cannot escape; or use a pie crimper.
Bring 4quarts water with ½tablespoon salt to a boil in a large pot, and gently drop in the triangles. After 5 minutes remove them with a slotted spoon. If a dumpling is not cooked, cook for a few minutes longer. Drain completely.
Brown the bread crumbs in butter until light brown, not too dark, and put the drained derelye in the crumbs. Mix carefully, just enough to coat them well. They will never have a “breaded” texture, so don’t worry if bread crumbs stick to only some parts of the dumplings.