The recipes you unlock in Hello Kitty Island Adventure require various food resources that you can pick up on Friendship Island. As you level up your friendship with the Island Adventure cast, more quests that unlock various tools will open up for you. The Chocolate Coins are one of many underwater resources that are inaccessible until you get the Flippers and the Snorkel. However, they're worth gathering, since they're used in two separate 3-heart gifts.