1

Stir together the flour, baking soda, and salt in a small bowl; set aside. With an electric mixer on low speed, beat the butter and sugar in a medium bowl until well blended. Add the egg white and vanilla; beat until smooth. Add the flour mixture and beat just until blended. Transfer half of the dough to a small bowl and stir in the orange zest. Stir the orange juice, cocoa powder, and grated chocolate into the remaining dough.

2

Pat the chocolate dough into a rectangle on a 12-inch-long piece of plastic wrap. Cover with another piece of plastic wrap. Roll out the dough to form a 5 x 8-inch rectangle. Repeat with the orange dough. Refrigerate the doughs about 5 minutes. Remove the top sheets of plastic wrap from the doughs. Flip the orange dough on top of the chocolate dough; remove the plastic wrap. Using the bottom sheet of plastic wrap to help you and beginning with a long side, roll up the dough, jelly-roll style, to form a tight log. Wrap in the plastic wrap and roll into a 9-inch-long log. Refrigerate until firm, at least 4 hours or up to 2 days.

3

Meanwhile, place the oven racks in the upper and lower thirds of the oven and preheat the oven to 350°F. Spray 2 large baking sheets with nonstick spray.

4

Cut the log into 1⁄4-inch-thick slices, making a total of 36 slices. Place on the baking sheets about 1 inch apart. Bake until golden brown, 8 – 10 minutes, rotating the baking sheets halfway through the baking. With a spatula, transfer the cookies to racks and let cool completely. Yields 1 cookie per ser serving.