> Oookay...how big is that? Go to the store and look at the onions. Categorize them as large/medium/small. Now you know what a small onion looks like. Additio

> Oookay...how big is that? Go to the store and look at the onions. Categorize them as large/medium/small. Now you know what a small onion looks like. Additional precision doesn't help here because onions aren't all the same. Two onions of identical size will contribute varying amounts of sweetness and pungency based on their freshness. The effect of your knifework and cooking temperature will make the outcome vary as well. "Add 200g of diced onion" is false precision. It looks more precise but it actually doesn't change the reproducibility of the dish at all. > How much of a difference in flavor will it be if I add more or less? Is onion a main ingredient like in onion soup? Probably a meaningful amount. Is onion just part of the overall mix? Probably not much of a difference. This isn't something that a recipe can tell you. This is something that learning to cook tells you. There is an entire genre of books that teach this "what makes recipes taste the way they do" concept but they aren't recipe books.