Combine finley chopped celery, roughly chopped potato, chopped spring onion and butter in a pot over medium heat, season with salt and cook, stirring until onion is tender, 8-10 minutes.
Add vegetable broth and bring to a roiling boil, turn heat down and simmer until potatoes are tender, for 8-10 minutes.
Turn the heat off, and blend the soup with 1/4 cup dill. If you want it creamier just add 1/2 cup heavy cream or add 1/2 cashews at the beginnig with the potatoes, but you don't need to! It's really delicious without it too!
If you add cashews to the potatoes, add some lemons juice, for the taste