Sift out flour, add salt and make a groove, put in the egg, add water and knead tight dough. Then cover it with a film and leave to "rest" for 30 minutes. For the filling, mince the pork and beef with the onion. Add milk, salt and pepper. Roll out thin dough and cut small disks with a glass. Put the filling in the center of each disk, then fold the dough in half and join up the edges to seal them. Pinch the corners together, dipping your fingers into the water. Flour the cutting board, lay pelmeni on it and put in the freezer. When pelmeni freeze up, they can either be cooked or put in a plastic bag and stored in the freezer.