1 cup (2 sticks) unsalted butter, softened
1/2 cup sugar
1 teaspoon pure vanilla extract
1/4 teaspoon pure lemon extract
1/4 teaspoon salt
2 1/2 cups sifted all-purpose flour
3 tablespoons Dutch-process cocoa powder
1 large egg


cream butter and sugar until well blended
Add vanilla extract, lemon extract, and salt.
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.

Shape and bake dough however you like in a log form, using the egg as a binder of the two halves.
(Either Checkerboard, Swirl, anything, doesn't really matter.)
Slice each log into 1/4-inch-thick slices; place on baking sheet. Bake until done, 10 to 12 minutes.