To make the koh fun if you cannot find it in your grocery store. Preheat oven to 350°F. Line a baking pan with parchment paper. Spread out glutinous rice flour across surface. Place in oven and bake for 10 minutes. Remove and stir around so flour cooks evenly and does not burn. Place back into oven for ten minute intervals until flour turns a light tan color indicating it has been cooked. This may take half an hour to an hour. I actually made more than 100g, so I would have extra flour to work with.

To make the mooncakes: Sift the koh fun and icing sugar in a mixing bowl. Gently rub the shortening into the flour mixture, combining until the mixture resembles coarse bread crumbs. Mix in the cold water about 1 tsbp at a time and knead dough until soft dough forms. You may need slightly less water or slightly more so dont pour it all in at once. It's best to knead the dough with your hands so that it comes together. If you wish to add in food coloring or flavor, add it in together with the cold water. Let the dough rest for at least 30 minutes before using. (please note, only do this if you are making your own flour. If you are able to buy the premade flour, don't let the dough rest as it will dry out) 

Divide dough, depending on size of mooncake molds. The ratio should be 1 part dough, 2 parts filling. So for a 100g mooncake, you would weigh out 30 grams of dough and 70 grams of filling. 

Flatten the ball of snow skin and roll out until you get a thin circle. Place the ball of filling in the center of the dough and seal the filling with the snowskin dough. You may need to maneuver and smooth it around. Put the ball seam-side up into the floured mould and pack it in gently. Flip it over onto flat surface. Press down on the lever hard so that the mooncake shape is formed and the face plate makes imprint. Then squeeze to release and your mooncake. Repeat with remaining dough. Chill for 6 hours before serving. Keep uneaten ones in the fridge.