Preheat the oven to 425 degrees
Chop the cauliflower into bite sizes florets and toss in the three tablespoons of olive oil
Place the cauliflower on a baking tray and roast in the oven until the florets are brown and fork tender, about 45 minutes
While the cauliflower is roasting, chop the white part of the leek and place in a strainer. Run under cool water, removing any dirt
In a medium soup pot, add the reserved one tablespoon of olive oil, the leeks and the garlic. Cook until the leeks are softened, about ten minutes
Once the leeks are softened, add the roasted cauliflower, vegetable stock, salt and black pepper. Cook on low for ten minutes
With an immersion blender, blend the soup until very smooth. If you do not have an immersion blender, place the soup, in two batches, into a blender and blend
I like to top my soup with toasted pumpkin seeds for an added crunch. Enjoy!