Two tips while dinner was being prepared.
Use a sieve or mesh strainer to disolve miso
Miso can be difficult to fully dissolve as it will clump up and physical agitation only goes so far.
Use Nameko Mushrooms to thicken soup - ナメコ
I didn’t see them before they were cooked.
Instead of the watery broth, it was silky with a slightly higher viscosity.