Chocolate Donuts is one of the accessories for mouth you can get in the game, it gives better stats than Romantic Flower or Cigarrette. This blueprint can be bought in Geffen Smile Asssistance.
The wearer will recieve Int +1, Str +1, Atk +5. By default this blueprint is locked, and can only be unlocked by a certain class, Crusader and Priest.
First you have to go to Adventure Hall in Prontera town.
Talk to Laiyinasi, she is the High Priest inside that hall.
Find Toukyou and get the quest from him. He's a Lord Knight.
For Crusader, you need to kill 40 Argiopes. Monk or Priest will be asked to kill 40 Menblatts.
Go back to Adventurer hall and sbmit the quest, this will unlocked the Chocolate Donut blueprint.