This recipe is is a savory appetizer (or often served as a light supper). It's popular in Russia and Eastern Europe. They're sort of like dumplings, but filled with beef. Since those are my dad's family's roots, I made some for him and he really enjoyed them. He said he recalled a similar recipe from his childhood that his grandmother and great-aunts used to make from time to time.
1For the filling, cook and stir beef with onion in 10-inch skillet until no pink remains in beef; drain. Stir in egg, dill (or parsley), salt and pepper.
2For the pastry, cut butter into flour and salt until dough resembles small peas. Stir in sour cream. Gather pastry into a ball. Divide dough into fourths; cover with damp towel to prevent drying.
3Roll each fourth into a 12-inch circle on a floured surface. Cut pastry into 3-inch circles. Place rounded teaspoonfuls of beef filling on center of each circle. Fold one side of pastry over filling, to form a half-circle. Dot pastry edges with water, and fold the bottom pastry over the top pastry about 1/4" (to keep filling in), and pinch edges to seal. Then fold the two ends in about 1/2 inch.
4Place, seam side down, on ungreased backing sheet. Repeat with remaining pastry. (Pastries can be covered and refrigerated no longer than 24 hours at this point.).
5Heat oven to 400°F.
Mix egg yolk and water, and brush pastries with the egg yolk wash. Bake about 15 to 20 minutes, or until pastries are golden brown.