Add a couple of tablespoons of water to a large saucepan and place it over a medium heat.
Add the onion, potato and celery. Pop on the lid and sweat for 5 minutes, stirring from time to time so the veggies don't stick. Add a little more water to the pan if they do.
Add the cashew nuts and the stock, scrapping up any browned bits from the base of the pan. Pour in half the dairy-free milk and add the celery salt.
Bring to the boil (be careful as it has a habit of suddenly boiling over if your back is turned!). Reduce the heat and simmer with the lid on for 20 minutes or until all the veggies are soft.
Turn off the heat and blend to smooth with a stick blender. Add more dairy-free milk as need to get the consistency you want (I like mine super thick!). Season with salt and pepper.
Serve with a garnish of fresh chopped parsley if desired.
