This recipe for chocolate cookies was sent to The New York Times several years ago by Mari Pfeiffer, a reader in California; it’s from the cookbook “Great Cookies,” published in 2003 by the author and teacher Carole Walter. The cookies are filled with deep flavor from the combination of cocoa powder, unsweetened chocolate and espresso powder. Decorate them with royal icing. “Other icings would spoil the cookie’s simple yet amazing flavor,” said Ms. Pfeiffer, who often cuts the dough into letters to spell out seasonal messages.