Mix eggs with sugar until light in color and fluffy
Melt the chocolate with the butter on a steam bath and let it cool a bit (I put the chocolate bowl in a larger bowl with a little ice water). When the chocolate has cooled long enough not to burn your finger, add it over the eggs and mix well.
Mix the flour with the vanilla sugar, baking powder and salt. Gradually add it over the chocolate cream, stirring constantly until it is completely incorporated and you get a dough with the consistency of a thicker cream.
Cover the cream with cling film and put it in the fridge overnight or at least 3 hours (I had to leave less because the guests were coming and I wasn't ready, but they turned out delicious anyway). When the cream has hardened, take it out of the fridge, take a spoonful of the composition and form balls that you roll first with sugar and then with powdered sugar. Place them on an oven tray lined with baking paper.
Bake in the preheated oven at 180 C / Gas mark 4 for 10-15 minutes, taking care not to leave more because they will dry too much.
GOOD APPETITE !!!