Make a well in the center of flour. Stir in rest of ingredients. Knead 10 minutes. Let rest covered 1 hour. Roll out dough on a floured surface, as thin as possible. Cut out 3 1/2 " rounds. Place 1 T filling into ea round. Baste edges with egg white. Fold in 2 pressing edges down to stick together. Cook in plenty of salted boiling water until they rise to the surface.