What is the purpose of this chest in the Sugar Daddy's room?

Question

The chest seems to still be unable to be opened before  and after killing the boss

Answer 1

You can open the chest after completing the Sweet Dreams Quest.

I got a Rainbow Waffles Recipe in it. 

According to Eudocia:

The recipes for the rainbow waffles, nightsky cupcake, matcha turtle and rose milk cake are flavour quest rewards and an invitation to bake those sweets. Perhaps someone wants to give it a shot.

Comments

never turned in the final part of the quest after receiving a feather! thanks!