First make the lard dough. Sift the flour and salt together, and then cut the lard into the flour until well mixed. Then add the water and knead the dough until smooth. Then make the lard cake by cutting the cake flour and lard together until well mixed. Set both aside.

Combine the ingredients for the ginger scallion water in an electric blender. Blend the mixture together until completely pureed. Strain the liquid using a mesh strainer and discard the fibrous residue. Set aside. In a medium mixing bowl combine all the filling ingredients and mix well.

Divide both the lard dough and lard cake into ten equal portions by rolling each into a long cylinder of about 1/2 inch diameter and cutting into equal pieces. Flatten one portion of the lard dough and roll it out with a rolling pin into a three-inch diameter round. Roll one portion of the lard cake into a ball and put it in the center of the lard dough. Wrap the lard cake with the lard dough and roll the dough into an oval shape sheet of about 1/8 inch thick. Start from one end of the long side of the oval and roll the dough into a cigar shape. Then us a rolling pin and flatten the cigar shaped dough into a flat ribbon. Once again roll the ribbon into a short cylinder. Flatten the cylinder and roll the dough into a round of about 1/8 inch thick.

Divide the filling into ten equal portions. Put one portion of the filling into the round dough. Wrap the filling completely by gathering the edge of the round and pinching tightly. Turn the mooncake and put the seam side down onto a greased baking sheet. Repeat the wrapping process for each portion of the dough and filling.

Preheat the oven to 375°F. Whisk the egg in a small bowl until completely mixed. Use a pastry brush to apply the egg wash to each of the mooncakes. Bake the mooncakes for 20 minutes or until golden brown. Serve immediately.