Clean the leeks: Remove the dark green parts and the root ends and discard. Cut the leeks in half and then slice them into half moons. Place in a large bowl of cold water and use your hands to agitate to remove all the dirt. Remove from the water carefully, making sure any dirt stays at the bottom of the bowl.
Put the vegan buttery spread, leeks, and celery in a large stock pot. Cook over medium heat until the vegetables are softened, about 6-8 minutes.
Add the potatoes and stock, and bring to a boil. Reduce to a simmer and let cook until the potatoes are tender, about 20 minutes.
Add the non-dairy milk and salt and stir. Puree the soup using an immersion blender. I like to leave some potato chunks in there - you can decide how smooth you want the soup to be.
Season with more salt and pepper if desired. Serve topped with fresh parsley and bacon.
Notes
This soup should stay fresh in the refrigerator for 3-4 days.If you don't have leeks, you can use regular onions.Feel free to leave out the bacon if you are vegan.