This page explains how to start and complete the Koko Cuisine side quest.
How to Start the Quest
Before you can start this quest, you must first complete the quest Cooking with Koko. Then you can talk to Koko outside of the produce store in Kakariko Village between noon and 7PM to start the quest.
How to Complete the Quest
Give Koko a piece of Raw Meat to complete the quest. You can get Raw Meat by hunting Woodland Boars, Mountain Goats, Grassland Foxes, etc. You will get a Tough Meat-Stuffed Pumpkin, and the recipe can be found in the record of the Cooking With Koko quest in the Adventure Log.