Preheat the oven to 350°F (180°C) and line an 8x8-inch baking pan with baking paper.
With an electric mixer, whisk together the avocado, eggs, butter, and Erythritol to get a smooth and lump-free batter.
In another bowl, combine the dry ingredients: the cocoa powder with the almond flour, salt, and baking powder. Whisk well.
Fold the dry ingredients mixture into the avocado batter. Add 4 tablespoons of the chopped chocolate and stir.
Pour the batter into the prepared baking pan.
Sprinkle the remaining dark chocolate on top.
Bake for about 20 minutes and allow to reach room temperature before cutting and serving.