So far we're only able to add enough ingredients to create one item of any instance, or we can add all the existing ingredients that we have to the slots that match the recipe. My suggestion is a third button, which allows us to input the number of cooking results we want. Want 3 potions? It adds the required amount of ingredients for 3 potions. Saves many the pain of having to keep track of the cooking times and not accidentally creating more results than was planned, as well as forgetting to keep clicking 'Add 1' every time.