Cooking and proficiency
Right, so cooking is a simple task - mostly. You'll need to go up to a cooking pot when it's not raining and light a fire under it with one of your Pyro characters - if you don't have many characters, just use Amber.
Once the pot starts cooking you can start, um, cooking. Just select which dish you'd like to cook - if the recipe is grayed out, that indicates you are lacking some of the ingredients, and you can buy those from a vendor in town, or find them in the overworld.
Each recipe has a proficiency. When you first start cooking you'll need to play a short minigame, but once you proficiency is maxed out, you can auto-cook many meals at once. Just cook the same meals over and over until the proficiency is maxed for each.
When your characters get knocked down it can be tough to revive them - certainly tougher than getting their health up in the first place. This is why cooking is important.
You can easily revive characters through cooking, even while in the middle of intense battles, and the most simple way to do this is via fried eggs.
You can find eggs in nests in trees, or on top of buildings, and each egg can turn into a fried egg. Fried eggs will revive downed characters with a small amount of health, and then you can use other meals to top up their HP.
Some of the recipes you cook up can have incredibly beneficial effects - while this isn't very important when you first start exploring Teyvat, it'll be vital when it comes to getting close to max level and clearing out those last few dungeons.
For example, some recipes will give you damage enhancements, or cut the amount of stamina required to navigate the world, making it much easier to get around.
These benefits are excellent, but as I said, not necessary in the early game. But still you should focus on collecting a variety of recipes so you're well prepared for those late-game challenges.
That's it! I've come up with a new recipe
To get a new recipe, all you need is, well, a piece of paper with a recipe on it. Use it at a cooking pot, and boom, you have a new dish to put together.
You can collect these from quests and chests, but some of them will just be from NPCs that you can talk to.
A particularly beneficial recipe can be found near Mondstadt - kind of. From Mondstadt head towards the North East and you'll find a woman walking along one of the high cliffs, and she'll give you a recipe with some excellent benefits…