Preheat the oven to 350°F. Line two baking sheets with parchment paper and set them aside.
In a large bowl whisk together the Chinese rice flour, potato starch, sorghum flour, cocoa powder, baking soda, baking powder, xanthan gum, salt, and powdered vanilla rice milk; set aside.
In a small bowl combine the water and cider vinegar. Set aside.
In the bowl of a stand mixer, cream the organic palm fruit oil shortening and dark brown sugar until fluffy. Beat in the applesauce and scrape down the sides. Add the dry ingredients alternately with the water and cider vinegar combination, starting and ending with the dry ingredients. Blend until smooth.
Using a small ice cream scoop, release the batter onto the prepared sheets. Bake for 10 to 12 minutes or until the cakes are firm to the touch and a toothpick inserted in the center comes out clean. Remove the finished cakes to cooling racks to cool completely.
When the cakes are completely cooled, frost the flat side with Supermarket Frosting and then place another cake on top to form a soft sandwich cookie.
Eat the whoopie pies immediately or store them, refrigerated, in an airtight container for 3 days.
In the bowl of a stand mixer, cream the organic palm fruit oil shortening and the powdered vanilla rice milk until they are light and fluffy.
Stir in the confectioners' sugar 1 cup at a time. The mixture will be crumbly.
Slowly stir in the water, salt, and vanilla extract and then beat the frosting for 3 minutes on medium high.
Use the frosting immediately or store it in an airtight container with plastic wrap pressed directly on top of it in the refrigerator for 3 to 5 days or, in the freezer for up to 3 months. Thaw the frosting completely and beat it again before using.