They said in an earlier chapter that Shinobu inherited the tongue of her family, so I imagine with Taisho's comment about her being a good taste tester she might have a sensitive palate akin to Erina from Shokugeki no Souma, though not as extreme.
Either you do it low and slow, like what's done in this manga, or you pressure cook it. I'm more of a fan of the low and slow way, always end up with nice broth too.