Beat the butter, sugar and eggs until light and fluffy and the sugar has completely dissolved. Add the hazelnuts, chocolate powder and milk and mix well. Mix the white flour, baking powder and salt, sieve into the beaten mixture, fold in and transfer to the prepared tin.
for approx. 1 hr. on the bottom shelf of an oven preheated to 180°C. Remove, allow to cool a little, remove the tin frame, slide onto a cooling rack, allow to cool and dust with icing sugar.