PREP: Cut the leeks in half through their stems, lengthwise. Rinse them free of any soil or sand trapped in between the layers, then chop both the green and white parts roughly. Dice the onion and cut the cauliflower into bite size pieces. Peel and trim the parsnips, then slice them finely. If the parsnips are especially thick, cut them in half lengthwise before slicing.
SIMMER: Add the chopped vegetables to a 6 qt dutch oven or similarly sized pan. Pour over the bone broth and add the salt, oregano, dill and garlic powder, then bring the broth to a simmer. Cook at an even simmer until the vegetables are fork tender, about 30 minutes. Add the arugula a little at a time until it is just wilted, then remove the dutch oven from the heat.
BLEND: Add the coconut milk to the dutch oven, then use an immersion blender to gradually blend everything together until smooth. For a super smooth soup as pictured, let the soup cool a little and carefully transfer the soup in batches to a high powered blender instead of using an immersion blender. Be careful to leave plenty of room in the blender and to leave a way for steam to escape when blending hot soup!