Dice pork butt into large pieces and season with salt and pepper.
Peel ginger and dice into large chunks.
In a bowl, mix 1 cup miso paste with chicken stock until well combined and reserve for later use.
In a pot over medium heat, add canola oil.
Add pork butt and cook until golden brown.
Add diced ginger and cook for 3 minutes.
In a bowl, mix 1 cup miso with chicken stock until well combined.
Add the miso chicken stock mixture to the pot. Let this cook for 1 hour or until the pork is tender.
Rough chop the watercress and add to the pot.
Season soup with salt and pepper, to taste.
Serve and enjoy!