Mix everything and microwave for 1~1 minute and 15 seconds.
Melt dark chocolate and butter over a double boiler.
Beat the egg, add erythritol, and mix together.
Combine the egg mixture with the melted chocolate mixture and mix well.
Sift in almond flour and cocoa powder, stir until evenly combined.
Pour the batter into a mold and bake in a preheated oven at 170°C for 25 minutes.
Let it cool and slice into bite-sized pieces.