In the middle of a 12-inch-long sheet of parchment paper, shape the cookie dough into a log that’s slightly wider than the desired diameter of the finished cookie.
Fold one side of the parchment over the log. Press a ruler firmly against the length of the dough while pulling the bottom of the sheet of parchment toward you. Continue pressing and pulling, making sure you apply even pressure, until the log is smooth and reaches the desired diameter.
Roll the remaining parchment around the log, then gently twist both ends closed. To prevent one side from flattening in the refrigerator, roll the log in a thick layer of wrapping paper if you’re gifting, or slit open the long side of a paper-towel tube and place the log inside.