Preheat the oven to 180°C.
Combine protein powder, unsweetened cocoa powder, and almond flour in a bowl.
Add eggs, unsweetened soy milk, and erythritol, and mix thoroughly.
Add baking powder to finish the batter.
Pour the batter into a mold and smooth it out.
Bake in the oven at 180°C for 20 minutes.