The Oven in Hello Kitty Island Adventure is one of several cooking stations that you can use to make gifts for your friends. You'll unlock this cooking station very early in your Island Adventure playthrough. Despite this, it may be some time before you can start using the Oven to its full potential. You can upgrade it by befriending Hello Kitty and raising her friendship level. Doing so will also unlock her Companion Ability, which is extremely useful for when you have to use the Oven to make 3-heart gifts.