Traditional Italian sweet cookie, served with coffee. They're pleasantly sweet but very hard. Maria's mother made these every Christmas.
Beat egg whites until stiff. Add vanilla. If used, stir in egg yolk. Work the beaten whites into dry ingredients with hands into a stiff dough.
Roll pieces of dough into rope, about 3/4" (1.5 cm) diameter, and cut at an angle into bite size pieces. Bake on greased cookie sheet at 400 approximately 15 minutes.
Adding the egg yolk will make the straccadente a little softer. If you want something supremely hard that needs to be dunked in coffee or milk to make it possible to eat, make it without the yolk. If you want something very hard, but that you might be able to crack with your teeth, add the yolk.