In a bowl, add flour, ground walnuts, and icing sugar. Add your egg and whisk with a fork. Add butter (room temperature), previously cut in small cubes to your bowl. Mix with your hands until everything is perfectly mixed and no flour crumbs remain. Wrap the dough and let it rest in the fridge for about an hour. Take a quarter of the dough and roll it like a sausage. Cut that dough into small bits, 1-inch large ½ an inch thick. Roll each one of them between your hands. Shape them like a crescent. Put your cookies on a baking tray with a parchment paper. Bake at 340°F (170°C) for 8-10 minutes or until the bottom of the cookies is brown. Let them cool down for 10 minutes before sprinkling them with icing sugar. Keep them in a box to enjoy when you feel like indulging yourself in these delicious cookies. My favorite way to eat them is with hot chocolate. :)
