In a dutch oven, heat to medium high. Add the onions, celery and carrots. Saute for 5 minutes, adding 1-2 tbsp of water to ensure it doesn't burn.
Add in the vegetable stock and lentils. Bring to a boil and cover and simmer for 20 minutes. Add your seasonings and cook for an additional 5 mins.
Using an immersion blender or high speed blender, process the soup until smooth. Add in the plant based milk or cashew cream if you want it even richer. Process and serve.