Delicately nubby from the texture of Earl Grey tea leaves, these cookies are strictly for adults. For the best flavor, use top-quality bulk tea. Serve the cookies with a cup of the tea, or any time you want a sophisticated cookie. Without tea leaves, they are a wonderful shortbread cookie that even children will love.

For a chocolaty variation, add unsweetened cocoa powder. The dough can also be rolled out and cut into shapes as directed at the end of the recipe.

Place the granulated sugar and tea leaves in the bowl of the food processor and grind for 1 minute, or until the leaves are very finely chopped. Add the butter, flour, cocoa (optional), and salt and process for about 45 seconds. Scrape down the bowl and break up any large clumps with the spatula. Process for another 15 to 30 seconds, until the dough looks uniformly dark and forms large, shaggy clumps. Dump the dough out onto a work surface and knead gently several times, just to bring it together.

Squeeze the dough into a log about 12 inches long and about 1 inch in diameter, and gently roll it back and forth until smooth. Don’t add flour if the dough is sticky—simply refrigerate the dough for 15 or 20 minutes to firm up the butter, then try again.

If you like, sprinkle the sanding sugar on the work surface alongside the log and gently roll the log in the sugar, turning to coat evenly. Cut a piece of plastic wrap several inches longer than the log and center the log at one long edge of the wrap. Roll the log into the wrap so it is tightly bound by the plastic. Twist the ends of the wrap to secure the log and help to create a rounded shape. You can use a cardboard paper towel roll to keep the roll of dough nicely rounded during storage. Just slit the cardboard lengthwise and slip the log inside it to help keep the rounded shape. Refrigerate for 2 hours.

Preheat the oven to 300°F and position an oven rack in the center. Line the baking sheet with parchment paper.

Remove the cardboard and plastic wrap from the dough log and use a thin knife to slice it into ⅜-inch-thick rounds. Place about 18 cookies 1 inch apart on the prepared baking sheet. Bake, rotating the sheet halfway through the baking time, for 30 minutes, or until the cookies are cooked through and look dry on top. (It’s difficult to tell when dark chocolate cookies are done. This is when an oven thermometer and a timer are your best friends in the kitchen.) Transfer the cookies to a cooling rack and let them cool completely.

Storing: Keep the cooled cookies in an airtight container at room temperature for up to one week.

Cutout Shortbread Cookies: Shape the prepared dough into a flat disk, wrap in plastic and refrigerate for 15 to 20 minutes to chill slightly. Lightly dust your work surface and the top of the dough with flour and roll the dough into a 10¼-inch circle about 3/8" thick. Alternatively, roll the dough between two sheets of parchment or wax paper.

Chill the dough again for 30 minutes. Cut into shapes using the cookie cutter of your choice and transfer to parchment-lined baking sheets.

To reroll scraps, brush any flour from the top and bottom of the dough, knead gently to bring together, and roll again. If the dough is sticky, chill it for 15 to 20 minutes and try again.

Once all the cookies are cut, transfer the baking sheets to the refrigerator and chill the cutout cookies for 30 minutes, then bake and store as directed.

Note: The size of your cookie cutter will affect the yield of the recipe, you may get only 1 to 2 dozen cookies.