Reserve 12 nuts for decoration and crush
the remainder. Whisk the egg whites until stiff. Add half the sugar
and continue to whisk until the mixture forms stiff peaks. Fold in the
remaining sugar, the ground hazelnuts and the vanilla essence. Spoon
the mixture into 12 rounds on a greased and lined baking (cookie)
sheet and place a reserved nut on the top of each one. Bake in a
preheated oven at 130°C/250°F/gas mark 1/2 for 2-3 hours until crisp.