Melt dark chocolate and butter using a double boiler.
Combine eggs and erythritol in a bowl and mix thoroughly.
Add the melted chocolate mixture to the egg batter and blend well.
Sift in almond flour and baking powder, then fold gently.
Pour the batter into a mold and bake in a preheated oven at 180°C for 25 minutes.
Let it cool completely, then cut into bite-sized pieces.