Spiced Chocolate Marble Shortbread

Preparation

1. Step 1

   Make the dough: In the bowl of a stand mixer fitted with the paddle attachment, combine the butter, sugar and salt. Beat on low speed until incorporated and smooth, scraping down the sides of the bowl as needed, about 3 minutes. (Do not beat until fluffy, you don’t need to incorporate air into the dough.) Add the yolk and mix until just combined. Turn the mixer off and scrape down the sides of the bowl.

2. Step 2

   Add the flour to the bowl all at once and scrape the bottom and sides of the bowl. Turn the mixer speed to low and beat until flour is fully incorporated, scraping the bowl again if needed, about 30 seconds. The dough will be in large crumbles.

3. Step 3

   Divide the crumbled dough into two portions (if the dough feels too crumbly to come together, mix in an additional egg yolk before dividing). To one half, add the cocoa powder and mix into the dough until evenly incorporated using a rubber spatula or your fingers. Use your hands to spread the chocolate dough on a sheet of parchment paper into a 7- by 10-inch rectangle. To the second portion of the dough, add the toasted sesame oil, citrus zest, ground ginger and candied ginger, if using, and mix until evenly distributed. Place the spiced dough on top of the chocolate dough and use your hands to spread in an even layer until it reaches all sides of the bottom dough.

4. Step 4

   Fold the dough in thirds similar to how you might trifold a letter: With the short edge running parallel to you, lift the right long side and fold it over until the right edge of the dough aligns with the center of the dough. Fold the left side over the top. Press down lightly on the dough to adhere the fold. Slice the dough lengthwise, down the middle, and stack the two halves on top of each other with the cut sides facing opposite directions. Press down again lightly to adhere. You should have what looks like a log at this point. Wrap the log in the sheet of parchment and refrigerate for at least 45 minutes and up to 3 days.

5. Step 5

   Heat the oven to 350 degrees. Line a sheet pan with parchment paper. Trim the edges of the chilled log by shaving off any rounded sides. Slice the log in half lengthwise to make two strips. Further slice each strip crosswise into ½-inch rectangles. Lay the pieces on the prepared baking sheet, spacing at least ½ inch apart. Bake until the cookies are golden at the bottom edges, rotating once halfway through baking, about 22 minutes. Move the cookies to a wire rack to cool completely. Store at room temperature in an airtight container for up to 3 days. The baked cookies can also be stored frozen in an airtight container for up to 5 days. Thaw at room temperature before serving.