Rank Equals Experience - Any character with the Rank of Guide (25) or higher may attempt an Ingredient Fix on their own troubled recipe.
Hauflins are Special - Any Hauflin (of any Rank) may attempt an Ingredient Fix on their own troubled recipe. Because they know about baking for the joy of it.
Help from Another - Any other Player Character (of any Rank or Class) who is also working in the Bakery may, if they choose, attempt the Ingredient Fix on your Character's behalf. The other player will re-roll the die.
Why don't we use [d6] <d8> {d12} to represent our dice rolls.
Let's say your character rolls [3] <1> {2}
Looks like they didn't add the right amount of Water or Flour (the d8 and d12 respectively). Sadly, there's nothing to be done here since the batch is too far gone to be salvaged from disaster. No Ingredient fix can be used here.
On the next turn your character rolls [5] <4> {11}
This time only one ingredient, Flour (the d12) was mixed in the wrong proportion. Now we need to see if there's any way to fix it, with a re-roll. Any one of the above conditions qualify so let's pretend this character happens to be a Hauflin. Bringing into play her natural baking abilities as a Hauflin this character may attempt a single re-roll for the wayward ingredient. She re-rolls her d12 (for Flour) and this time gets a {9}. Well done. The job wasn't quite up to Pennyblum's usual standards but she is willing to pay 2 Copper Pieces for the bread, which will probably end up in the decorative discount bin.
In our last example let's say your character, a Malornian rolls [6] <3> {10}
In this case only Yeast (the d6) was mixed in the wrong proportion. This means the batch can still be rescued with a little help, or a little more concentration. Our determined Malornian is merely a Novice in Rank and so he is left to rely on his fellow adventurers, a few of whom happen to also be in the bakery at the time.
He may now take a moment to see if any of them are willing to lend a helping hand by re-rolling the one ingredient die (the d6). Since the attempt can only be made once, regardless of all other conditions, only one other player may even attempt the fix. Once he has a willing volunteer the attempt may be made. As before, any successful fix earns our character 2 Copper Pieces. If the attempted fix is unsuccessful then that is that and there's nothing more to be done about it.
What about Companions? Of course. Well, companions are as varied as they come, which is to say that some are willing to help with genuine skill, others are willing to help with misguided aplomb while others are (as usual) preoccupied with other distractions. The thing to understand is that whatever your character's original roll for the bread baking can be thought of as a reflection of your companions' contributions (or lack thereof) for better or for worse. They don't come into play when it comes to The Ingredient Fix, even if one of the companions happens to be a Hauflin or a character of apparently high Rank.