In a large mixing bowl, add the almond flour, erythritol, coconut flour, baking powder, and salt. Mix well.
Add the butter and eggs, and mix to a sticky dough.
Split the dough in half, place one half between 2 sheets of parchment paper and roll our 5mm/0.25in thick. Using a saucepan lid and a circle cutter, cut out a thick ring and remove the excess dough. Repeat to make a second cookie ring. Use the leftover dough to make mini cookies for decorating your cake.
Transfer the rings to cookie sheets and bake for 12-15 minutes until the edges are firm.
Place the cookies on cooling racks and leave to cool completely.
In a mixing bowl, add the mascarpone and heavy cream, whip with a hand mixer until combined.
Add the vanilla and turn the mixer to medium speed, then add the powdered erythritol a spoonful at a time until it is all mixed in. Whip until the mixture reaches stiff peaks.
Spoon the cream mixture evenly into 2 piping bags.
Place one of the cooled cookies onto a cake board or serving platter.
Pipe 1 bag of the cream mixture on the cookie, using any technique or design your like. Place the raspberries evenly around the edge.
Top with the second cookie and pipe over the remaining cream mixture.
Decorate your cake with mini cookies, fresh berries and colored chocolates and shards, if desired.
Chill in the fridge for at least 1 hour before serving to help soften the cookies.