Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper. In a mixing bowl, combine the brown rice flour, tapioca flour, and cocoa powder. In another bowl, whip aquafaba with a hand mixer until soft peaks form. Gently fold the whipped aquafaba into the dry mixture until just combined.

Pour the batter onto the prepared baking sheet, spreading it evenly to about 1/2 inch thick. Bake in the preheated oven for 25 minutes, or until the sponge springs back when lightly pressed.

While the cake is still warm, carefully lift it out of the baking sheet using the parchment paper. Place it on a wire rack to cool for about 15 minutes.

Prepare your chosen filling by blending chestnut puree or a mix of oat cream, vanilla extract, and cornstarch in a blender until smooth. Taste and adjust with maple cream if desired.

Spread your filling of choice generously over the cooled sponge, leaving a small border around the edges. Starting from one short end, carefully roll the sponge into a log.

While the cake is chilling, make the chocolate ganache. Melt dark chocolate and whisk in a splash of oat cream over low heat until glossy.

After chilling, remove the log from the refrigerator and drizzle or spread the ganache over it. Decorate with fresh cranberries and a dusting of powdered sugar before serving.