Whisk the egg whites with a pinch of salt until they are stiff.
If ground walnuts are not available where you live, simply place the same weight of whole walnuts in the food processor and blitz until they are finely processed.
Add the ground walnuts, ground hazelnuts and sugar to the egg whites.
Mix everything together to form a sticky dough.
Roll the dough out between two sheets of baking paper until it is about 1 cm thick.
Use a cookie cutter of your choice (e.g. flower, Christmas tree, star) and cut out your shapes, re-rolling the mixture as needed. As the dough is fairly moist and sticky, you might need to use a palette knife or spatula to lift the cookie shapes.
Place the shapes on a sheet of baking paper and leave them to dry for about 6 hours or overnight.