Roughly chop the chocolate. Melt butter and chocolate in a saucepan over low heat while stirring, remove from the heat and pour into a mixing bowl. Separate 3 eggs, chill the egg white.
Add 150 g sugar, vanillin sugar, salt, egg yolks, 2 eggs, flour, milk and baking powder. Mix with the whisk of the hand mixer to a smooth dough. Place paper baking cups in the hollows of a muffin tray (12 hollows).
Pour in the dough and bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 15 minutes. Beat the egg whites until stiff, adding 150 g sugar. Sift the cocoa over the egg whites and fold in.
Pour the mixture into a piping bag with perforated spout. Increase the temperature of the oven (electric oven: 200 °C/ circulating air: 175 °C/ gas: level 3). Take out the muffins, spray meringue mixture in tuffs onto the muffins.
Put the muffins back in the oven and bake for 5-6 minutes. Remove muffins from the oven and let them cool on a cake rack.