Beat eggs and sugar until light yellow.In a saucepan heat butter and dark chocolate, chopped in small pieces.Keep the fire very low and mix from time to time, pay attention not to burn it.
Let the chocolate cool down a little then pour it slowly into the egg mixture, mixing well.
Add now salt and the flour sifted with the baking powder.Knead until you have a smooth loaf.Cover with cling film and let it rest in fridge for at least two hours.
Make small balls out of the dough then roll them into the icing sugar and put them on a lined baking tray.
Bake at 340°F for 8-10 minutes.They will be very soft straight out of the oven, let them cool down before touching them.