Preheat the oven to 180°C.
Melt dark chocolate and butter together over a double boiler.
Add eggs and erythritol to a bowl and mix well.
Pour the melted chocolate mixture into the egg mixture and combine.
Sift in almond flour, baking powder, and salt, then mix thoroughly.
Top the dough with chopped walnuts.
Shape the dough into round balls and place them on a baking tray.
Bake in the oven for 12 minutes.
Let them cool down before serving.