Preheat oven to 450 degrees
In large bowl, add chopped nuts, sugar, semolina and baking powder and mix well. To this add the vanilla extract, cognac, grated orange rind and 2 egg yolks and mix well.
In separate bowl beat egg whites until stiff peaks form.
Slowly add the egg whites to the nut mixture a little at a time to form a pliable mixture. It may not take all of the egg whites, so be sure to do this slowly as yo do not want a dough that is too wet.
Butter a baking sheet with melted butter.
Take a piece of dough and shape it into the form of a half moon and place on cookie sheet. Continue making cookies, spacing them slightly apart. Bake for 10-15 minutes. Cookie will remain soft when removed, and will set when cools. Let cool slightly and dust heavily with powdered sugar.