Melt the vegan butter in a large soup pot on medium low heat. Add in the onions and celery and sauté for 3-5 minutes or until the onion are translucent.
Add in the potatoes, garlic and cook for 2 minutes or until the garlic is fragrant. Add in the flour and mix until everything is well coated. Cook the mixture for 1-2 minutes while stirring. Add in the broth and plant milk and mix well. Cover the pot and simmer for 25 minutes or until the potatoes are fork tender.
Using an immersion or regular blender, blend about half of the soup. Make sure to leave some potatoes unblended in order to create a creamy and balanced texture.
Add in the vegan sour cream and mix well. Allow the soup to heat through for another 10-15 minutes on low heat. Serve with additional vegan sour cream, shredded vegan cheddar, chopped vegan bacon and green onions.