Does this method work with other flavourings? My partner doesn't like the miso, so I want to split into two batches and flavor separately (bc I st...

No, this method is actually really unique to the miso. The enzymes in the miso paste work to break down the starches in the oats, making them taste sweeter. The final product shouldn't taste super miso-y; you're using white miso, which is the mildest kind, and only a little bit. It's not in there for flavor so much as it is for the way it transforms the oats through enzymatic action.

I'd suggest using an even smaller amount of miso if your partner isn't into that flavor. There are tons of enzymes in even a tiny tiny dab of miso paste, so you could put in enough to get that effect, but not the flavor effect. And if you like the flavor, you could add more miso to your own portion in the morning!

The miso is not critical to how this recipe cooks. Simply add salt to the bowl without miso! Parmesan cheese could also be a good substitute.