Starting the Quest[]
Speak to the Cook in Lumbridge Castle to start the quest. The Cook will explain to you that he needs to prepare a cake for the Duke's birthday and needs help gathering the ingredients.
Obtaining the Items[]
After agreeing to help the cook you'll need to gather an egg,a bucket of milk, and a pot of flour. These items can be gathered around the Lumbridge area, found in the diagram below.
Completing the Quest[]
After you have collected all the items, return back to the Cook and give him the items to complete the quest.