Players can turn a chocolate bar into chocolate dust by grinding it with a pestle and mortar (members) or a knife, awarding the player with 1 Cooking experience. This is also a slow, yet effective way of making money via the Grand Exchange. Members can make an energy potion by combining harralander in a vial of water and then adding chocolate dust. Members can also brew chef's delight. Chocolate dust can be used on a cake to make a chocolate cake the same way a chocolate bar can be.
When turning the chocolate bar into chocolate dust while in a free to play server, it used to show your character using a pestle and mortar even though the character would actually use a knife because pestle and mortar is a members only item.