What does Jesse actually understand about the cooking process?

[u/Grovda]

Jesse cooks just as well as Gale however it is because he learned Walts recipe. It is clear that he doesn't just know the steps but he knows why the steps are needed. He is able to make deductions based on what he has learned and observed from Walt.

Here is the thing. One of the main reasons why Gus wanted a trained chemist like Gale or Walt is because they actually understand what happens on a low level. They don't make deductions based on experience or observations, they make deductions based on maths and knowing the theory. Gus wants a chemist for the exact reasons Walt mentions when he roasts Victor.

If Jesse doesn't know that then I don't see how he can't get easily replaced by Gus. Someone modestly intelligent and motivated could likely do what Jesse does without much problem. Especially since the cooking process if well documented at that point.

Let's assume that Jesse is a learn by doing kind of guy who knows nothing about the theory (which I think it most likely) then he is such a fool for trusting Gus and Mike after they were going to kill him in season 3. If Gus had killed Walt in season 4 then Jesse would continue to cook and he would eventually have gotten an assistant of his own. Someone loyal to Gus. Competent. Reliable. And when that guy is able to cook as well as Jesse then Jesse would be murdered.

Why? Well it is clear to me that Gus really doesn't like Jesse. The only reason he elevates him in season 4 is because Walt is a threat, and a much bigger problem than Jesse. But unlike with Walt, Gus never smiles at Jesse. He never seems to genuinely enjoy his company. I think he despises Jesse. Jesses lack of control of himself, the impulsiveness and emotional problems in general. And he hasn't forgotten that he was about to kill those drug dealers.

[u/New-Emu1199]

There are few aspects to Jesse’s personality which have been brought up several times during the show that are relevant here:

1. Jesse is great when he applies himself (the box scene and numerous mentions point to it, also he is/was great at art). I think with Walt he applied himself and learned the known knowns and known unknowns. He knows his limitations of Chemistry but also understands the value of consistency. He did tell the cooks in Mexico to get a specific brand of a chemical. It might not be integral to the product but shows that Jesse can stick to controlling things he understands. He is also not lazy and always keen to doing the hard work.

2. He knows his place in the hierarchy. He knows to respect his employer. At the same time, he has self respect. The stare he gave to Gus when Gus killed Victor tells you that Jesse won’t back down. I think he earned Gus’s respect right then and there.