Sift together flour and salt. Combine eggs and water in a large mixing bowl, beating well. Gradually add flour mixture to egg mixture, stirring well to form a firm dough Cover and let rest 20 minutes.
Sauté onion in butter in a heavy skillet until tender. Add meat: cook over medium heat until meat is browned, stirring to crumble. Stir in mushrooms, sour cream, and salt; set aside.
Turn dough out onto a lightly floured surface, and divide into 16 equal portions. Shape each portion into a ball. Roll each ball into a 4 inch circle, Place 1 tablespoon meat mixture in center of each circle. Moisten edges of pastry with water; fold pastry in half. Press edges together with fork tines to seal.
Place turnovers, a few at a time, in boiling salted water. Cook 5 minutes; drain on paper towels. Transfer to a 13- x 9- x 2-inch baking dish. Pour Sour Cream Sauce over turnovers; bake at 375° for 20 minutes.