Preheat oven to 350°F. Grease a round 8-inch cake pan and set aside.
In a large bowl or stand mixer, combine the almond flour, sweetener, baking powder, and unsweetened cocoa powder.
Add the eggs and vanilla and mix to combine.
With the speed on low, slowly add the melted butter and mix until fully combined.
Transfer the batter to the prepared cake pan.
Bake the cake on the middle rack until a toothpick inserted in the center comes out clean or mostly clean, about 25 minutes.
While the cake is baking, prepare the Sugar-Free Keto Cool Whip according to recipe instructions. Roughly chop the dark chocolate squares. Add half to the whipped topping and reserve the other half for decorating the cake.
Put the frosting in the fridge so it stays cold until you're ready to use it.
Let the cake cool completely on a wire rack before frosting, which typically takes about 1 hour. Once cooled, cut the cake in half like a hamburger bun.
Create the middle layer by placing a large dollop of frosting on the top of the bottom cake layer.
Place the top layer of cake on top of the frosting layer. Frost the cake with the remaining frosting. Decorate the top and sides of the cake with the remaining chocolate pieces. Serve as is or chilled.