In a large soup pot or pressure cooker, heat olive oil over medium heat. Add the sliced leeks and stir for 2 minutes, careful not to let the leeks brown.
Add crushed garlic and celery. Stir and cook for 3 more minutes or until celery starts to soften. Add salt, pepper, thyme, and cauliflower. Stir and mix ingredients well.
Add vinegar and water to cover cauliflower (more water may be added if needed) so water is covering about 1/2 inch above vegetables. Cover pot and cook over medium-low for about 20-25 minutes, or until cauliflower is soft. If using pressure cooker, cover and cook for 5-6 minutes.
When cauliflower is soft, add the fresh tarragon and parsley, stir. Remove 1 cup of soup from the pot and add it to a blender with the cashews. Add some more of the soup to the blender and puree until smooth. Pour out pureed soup into a clean pot. Continue to puree the soup in batches until all is blended. Stir to combine cashew cream with rest of the soup. Add more water for a thinner consistency.
From The Whole Life Nutrition Cookbook (2nd ed.) by Alissa Segersten and Tom Malterre (Whole Life Press, 2008).