Preheat oven to 350 degrees. Line 2 baking sheets with parchment paper or silicone baking mats.

Combine the coconut milk and vinegar or lemon juice and stir. Let sit for 5 minutes.

In a large mixing bowl, whisk together the rice flour, potato starch, sweet rice flour, tapioca starch, xanthan or guar gum, cocoa powder, salt and baking soda.

In the bowl of an electric mixer, preferably fitted with a paddle attachment, cream the butter substitute with the brown sugar until fluffy, about 3 minutes. Add the egg and blend well, scraping down the sides of the bowl. Turn the mixer to low and add half the flour mixture, the coconut milk mixture and finally the remaining flour mixture. Add the vanilla and mix well.

Scoop about ¼ cup of batter for each cake and mound on the prepared baking sheet (a large ice cream scoop works well for this) leaving about 2 inches of space between each cake. Bake for 12 – 14 minutes or until the tops have puffed up and the cakes feel firm to the touch. Let cool on the baking sheet for 5 minutes then transfer to a wire rack to finish cooling. Let cool completely before filling.

In the bowl of an electric mixer, preferably fitted with a paddle attachment, mix the filling ingredients together on medium speed until smooth.

Pour the gluten free graham style cracker crumbs onto a plate. Place about 1 tablespoon of filling on the flat side of half the cakes. Top with the remaining cakes and press gently. Roll the filling-sides in the cracker crumbs letting them stick to the filling.