This wonderful holiday recipe for shortbread uses basic shortbread as its base.
Dissolve espresso powder in hot water. Prepare basic shortbread, adding espresso to creamed butter mixture along with vanilla extract before adding flour mixture. Form dough into a disk; wrap in plastic, and refrigerate for at least 1 hour (or overnight). Roll out dough to a 1/4-inch thickness. Cut into 2-inch rounds. Score a line down the middle of each with the back of a knife; refrigerate for 20 minutes. Bake until firm, about 20 minutes.
Cookies will keep, in an airtight container, at room temperature for 2 weeks.