In a pot, bring the water and sugar to a rolling boil. Keep it bubbling for a full three minutes, then turn off the heat and stir in the lemon juice.

Pour into a 9×13-inch dish or any container with a wide base and freeze for 12–24 hours.

Break into pieces and blend in a food processor fitted with the S blade on high speed until very slushy, three to five minutes. Stir in the mint by hand (if using) and fill the mold. Freeze for 24 hours.

Remove the sorbet clouds from the mold, garnish with lemon and mint, and serve.