It has a low drop rate.
Hunting for Chocolates
Only hunting zones level 70 and above will have a chance to drop Chocolates. When you defeat a monster, it has a chance to spawn an event monster and upon defeating the event monster, it has a low chance to drop a Chocolate. Chocolates can also be purchased from the L2 Coin Shop for 1,000,000 Adena with a limit of 20 a day.