Preheat the oven at 160°C/320°F. Line a baking sheet with parchment paper.
Combine flour, sugar and processed walnuts. Rub in the butter until the mixture is crumbly. Add vanilla extract, egg and mix to form the dough.
Make small ropes, curve them up and thin down the ends, so that they look like half moons.
Bake for 8-10 minutes. You should monitor the baking time very closely so they do not turn golden, they just need to dry out.
Put some powdered sugar in a ziplock bag. When the cookies are done, pop them immediately into the bag, so that they get fully coated. Then take them out of the bag and let them cool completely.
Once cooled, store them in an air-tight container for at least two weeks.
