Put the butter in a pan and heat until you have a beurre noisette. Take off the heat and leave to cool.
sift the flour into a bowl and then add the ground almonds and mix well.
Put the egg whites and sugar into a large bowl and whisk gently until fully combined, do not whisk too much, you don't want it to be aerated.
Fold the dry ingredients into the egg white and sugar mix, then mix in the cooled beurre noisette, mix until fully combined. Put the batter into an airtight container and place it in the fridge for an hour.
Preheat the oven to 170C, take the financier batter out of the fridge, it with have really thickened. Fill your moulds until they are three-quarters full, top with the chopped hazelnuts and bake for 15 minutes or until a light golden colour.
Leave to cool and then remove from the moulds and dust with icing sugar