Creamy Cauliflower Potato Leek Soup

In large bowl of water, soak sliced leeks to remove dirt. Drain leeks and lightly dry on a clean towel. In a large pot over medium heat, heat oil. Add leeks and onion to saute until softened, then add garlic and saute until fragrant. Add potatoes, cauliflower, salt, thyme, rosemary, and coriander and stir to combine. Add vegetable broth, bay leaf, and pepper. Increase heat to bring the mixture to a simmer. Reduce heat to low and cook for about 15 minutes, until potatoes are fork tender. Remove pot from heat and discard bay leaves. Stir in coconut milk and optional lemon juice. Using an immersion blender, blend until smooth and creamy. If needed, a regular blender can be used to blend the soup in small batches. Serve with fresh ground pepper and optional chopped green onions and grated cheese.