In a large soup pot heat the tablespoon of oil over medium heat. Add the leeks and sauté until soft and beginning to brown.

Add the potatoes and zucchini. Fill the pot with the vegetable broth or water to just above the height of the vegetables. Add in the spices and mix. Bring to a boil and then simmer, covered, for two to three hours.

Using an immersion blender, blend until smooth and creamy.