I first saw these cookies on Martha Stewart's website and became intrigued. I thought they looked like a lot of trouble and stashed the idea in the back of my mind. I volunteered to make cookies for the Fall Festival at my church and decided to give these a try. Yes, indeed, they are a bit of trouble. I think if you were making several batches at once, it would be much more efficient. However, the results were rather visually appealing (though perhaps not as perfect as Martha's). I didn't have Dutch process cocoa powder, so the flavor was a bit off (according to my husband). However, I think the kids will enjoy them nonetheless.
1 cup (2 sticks) unsalted butter, softened
1/2 cup sugar
1 teaspoon vanilla extract
1/4 teaspoon lemon extract
1/4 teaspoon salt
2 1/2 cups sifted all-purpose flour
3 tablespoons Dutch-process cocoa powder
1 large egg
In the bowl of an electric mixer fitted with the paddle attachment, cream butter and sugar until well blended, 1 to 2 minutes. Add vanilla extract, lemon extract, and salt. With mixer on low speed, gradually add flour, scraping down sides of bowl.
Turn dough out onto a clean work surface; it will be loose and crumbly. Knead dough by pushing small amounts away from you with the heel of your hand for 1 to 2 minutes. Divide dough in half. Sprinkle cocoa powder over one of the halves. Knead until cocoa has been fully incorporated. (This step can be avoided if making two batches; just add cocoa to one batch and leave the other plain.)
Place each half of the kneaded dough between two sheets of plastic. Using a rolling pin, shape dough into two 7-inch squares, about 3/8 inch thick. Using a sharp knife and a ruler, slice each square into nine 3/4-inch-wide strips.
Whisk together the egg and 1 tablespoon water. Cover work surface with plastic wrap. Place three strips of dough on plastic, alternating white and chocolate strips. Brush tops and in between the strips with egg wash. Gently press strips together. Repeat, forming second and third layers, alternating colors to create a checkerboard effect. Wrap assembled log in plastic. Repeat process for second log, reversing color pattern. Refrigerate 30 minutes, or freeze 15 minutes.
Preheat oven to 350F; line a baking sheet with a silicone baking mat or parchment paper. Slice each log into 1/4-inch-thick slices; place on baking sheet. Bake until done, 10 to 12 minutes. Remove baking sheet from oven, and let cookies cool 2 minutes. Transfer cookies to a wire rack to cool completely.