Set your 6 QT electric pressure cooker to sauté, add leeks and celery with a little water or broth to prevent sticking. Stirring frequently, sauté for 6-7 minutes or until leeks are tender.
Add the garlic, garlic powder, onion powder and salt substitute. Saute for about another minute.
Add potatoes, broth and sprigs of fresh thyme. Put lid on, cook on high pressure for 5 minutes, quick pressure release.
When pressure is released, remove about 3 cups of the potatoes and set them aside. Remove fresh thyme sprigs, add 2 cups of unsweetened plant milk.
Using an immersion blender, blend the remaining soup until smooth and creamy. Add the reserved potatoes back to the pot, add freshly ground black pepper if desired. Stir to incorporate all of the ingredients. Add more milk or broth if you want a thinner soup. We like it thick and with chunks of potato. If you prefer you can blend it all until smooth.
If you don't have an immersion blender, carefully transfer soup to a regular blender and blend to desired consistency.
You can add frozen corn or peas, chopped greens, or wild rice. Garnish with fresh thyme or chives. Serve with a fresh green side salad. Leftovers will set up and get thicker in the fridge. Add broth, water or plant milk to thin it when reheating. I do freeze some for future meals.
