Buttermilk Delight

Buttermilk Delight is a food candy that can be obtained during the Love is in the Air seasonal event.

Source
Randomly found inside a. The Box of Chocolates contains six items randomly selected from a list of five; four chocolates, including this one, and an empty wrapper. Odds favor getting a selection of three of the chocolate from any one box, but other combinations are common as well.

Achievements
You must consume one of each of the four chocolates to complete the achievement. Since they bind on pickup, you must obtain your own Box(es) of Chocolates. It typically takes two Boxes of Chocolates to complete this achievement, but getting all four chocolates in one box is by no means rare, and it can require several Boxes of Chocolates to get that last one.

You must consume one of this particular chocolate, while seated with another person at a in Dalaran to complete the  achievement.