These cookies are very easy to make and are absolutely delicious. I did use hazelnut flour because I didn’t have hazelnuts at home. Though, if you do have hazelnuts to grind, I’d suggest you use those because they would deepen the flavor even more. The espresso powder complements the nuts and the chocolate perfectly. I made a mistake reading the original recipe from America’s Test Kitchen. I made a very thick chocolate ganache using too much chocolate for the amount of cream indicated. The ganache should have been thinner, and, although I didn’t have any more chocolate left to melt and decorate the cookies, I think that the ganache came out perfect. Sometimes mistakes turn out fine.