Eat 100 Noblegarden Chocolates during the Noblegarden celebration.
The Noblegarden Chocolates required for this achievement are collected from Brightly Colored Eggs that are found during Noblegarden around each race's second town (first proper town after starting area): Azure Watch, Bloodhoof Village, Brill, Dolanaar, Fairbreeze Village, Goldshire, Kharanos, and Razor Hill.
Chocoholic requires you to eat 100 chocolates. You will also pick up the achievement Chocolate Lover -- which requires eating 25 -- along the way.
These chocolates (pre-eaten only unfortunately) can also be used to purchase various rewards like Swift Springstrider, Spring Rabbit's Foot, Tome of Polymorph: Rabbit and various outfits from Noblegarden Vendors.