Preheat oven to 350 F and lightly grease two 8" round cake pans.
To a bowl, mix the flax and almond milk and allow to sit in the fridge for 15 minutes.
To a stand mixer, mix the almond flour, cocoa, coconut flour, baking soda, and salt. Add in the maple, butter and the flax eggs and continue to mix until well incorporated. Manually mix in the chocolate pieces and the mint extract to taste.
Divide between the two cake pans and bake for 30 minutes, until dry on the top. Allow to cool completely to room temperature.
Meanwhile, add the butter to a clean standmixer and process until fluffy. Add in the powdered sugar, about 1/2 cup at a time until it reaches a thick buttercream consistency. Add the almond milk to thin it out just a touch and the mint extract and food colouring, to taste and appearance preference.
Once the cakes are cool, invert one out onto a plate or cake platter. Top with about 1 cup of buttercream and cover the top. Top with the other cake layer and do a rough and thin "crumb coating" with about 1/4 of the remaining frosting. Transfer to the fridge for 15 minutes.
After 15 minutes of chilling, add the presentation layer of frosting all around the edges and top of the cake. If there is extra, you can fill a piping bag to make little rosettes around the edge.
To decorate, add chocolate shavings and cacao nibs around the sides and on top. Enjoy!