Place the egg white into a small ramekin. Using a fork, stir 1 teaspoon of water into the lightly beaten egg white. Using a small paintbrush, lightly coat one lemon thyme sprig with egg white (the sprig should not be dripping); sprinkle the sprig with the superfine sugar, shaking off excess. Place sprig onto parchment or wax paper to dry. Sprigs may be crystallized in advance, thoroughly dried, and stored in a plastic container for up to 1 week; however, they look best when used within 24 hours. Do not refrigerate.
Excessive humidity melts sugar, so it is important to keep the crystallized sprigs away from humidity. Also, make sure they are thoroughly dried before storing in an airtight container.