Preheat the oven to 180°C (356°F).
Mix protein powder, cocoa powder, almond flour, and baking powder in a bowl.
Mash the banana in a separate bowl and add soy milk, oligosaccharide, and coconut oil. Mix well.
Combine the two mixtures and stir until evenly combined.
Pour the batter into a baking pan and spread it evenly.
Bake in the oven at 180°C for 20 minutes.
Let it cool completely, then cut into desired serving sizes.