Cooking With Koko
After completing the sidequest "Koko's Kitchen, which you can learn about here, talk to Koko again between noon and 7:00 PM outside the Kakariko Village general store. Again, it cannot be raining.
This time, Koko wants Goat Butter. You can buy it from the general store she is standing by. Just buy one and then give it to her.
As a reward, Koko will give you a Hot Buttered Apple. You will learn another recipe in your Adventure Log. Cook apples with goat butter.
The next sidequest is Koko Cuisine.