Taking a while is fine, that gives Shinji enough time to finish setting up pretty much anything else that can be set up right away. And then after that, he waits. And watches. He won't interrupt Kai's sincere efforts if he doesn't ask for that help, and he's patient enough to not rush him.

So

he waits

until the meat chopping is done.

Good job, Kai. You did it. "Yeah, I can start cooking that, if you want to do the vegetables next."

That, uh, took a little while, though, so maybe he shouldn't get the meat started, like, right away if he wants to keep the timing of everything nice and tight.