Beat the butter in a large bowl with a mixer on medium speed until smooth. Add the granulated sugar and beat until pale and thick, about 5 minutes. Whisk the egg yolks, vanilla and corn syrup in a bowl, then add to the butter mixture and beat until fluffy, about 2 minutes. Turn off the mixer and add the flour; pulse, turning the mixer on and off, until just combined. Transfer half of the dough (about 2 packed cups) to a sheet of parchment paper.
Mix the coffee liqueur and espresso in a small bowl, then add to the remaining dough in the mixer along with the chocolate, pulsing until combined. Transfer the chocolate dough to another sheet of parchment paper. Pat each portion of dough into a 10-by-6-inch rectangle and cover with another sheet of parchment paper. Refrigerate until firm, about 1 hour.
Roll out each portion of dough between the parchment sheets into a 12-by-8-inch rectangle, about 1/4 inch thick. Peel off the top parchment sheets and carefully invert the lighter dough onto the darker dough. Run a rolling pin over the dough to press it together. Refrigerate until firm, at least 30 minutes.
Roll over the dough a few more times to make it slightly thinner, then peel off the top sheet of parchment paper and trim the dough into an even rectangle. Position the dough with a long side facing you and roll it away from you into a tight spiral, using the parchment paper to help. (The dough should be just soft enough to roll; chill or let stand at room temperature as needed.) Wrap the log with the parchment paper and freeze until firm, at least 1 hour. (The dough will keep in the freezer for up to 2 months.)
Preheat the oven to 325 degrees F. Line 2 baking sheets with parchment paper. Slice the log of dough into 1/4-inch-thick rounds; place about 1 inch apart on the prepared baking sheets. Sprinkle with the raw sugar, if desired. Bake until the cookies are firm and lightly browned, 15 to 20 minutes. Let cool 2 minutes on the baking sheets, then transfer to a rack to cool completely. Store in an airtight container up to 4 days.
Photograph by Steve Giralt
Recipe courtesy Food Network Magazine