Melt the butter for the cake. 
Whisk egg and sugar till white and puffy.
Sieve the cacao, baking powder, flour and vanilla into the eggs. Add the melted butter.
Carefully spread the batter into a large baking tray, lined with greaseproof paper.
Bake in the bottom of the oven for 20 minutes in 200°C.

Let the cake cool down while you make the butter cream.

Mix the almond granules in a food processor, add drops of water until it becomes an almond paste. Add icing sugar, egg yolks and butter and continue mixing to a smooth cream. Spread the cream evenly on your cake. Cover and put in the freezer for 1-2 hours.

Melt the chocolate and mix with the oil. Spread on top of the frozen butter cream and let set (preferably in the fridge).

Cut the cake in approximately 5×5 cm squares and cut each square diagonally to two triangles. This cake is rich so best served in smaller pieces.

Keep in fridge to avoid buttercream to soften. Freezes well.

* increase if you wish a thicker layer of chocolate on top