First, cut apart a head of cauliflower and drizzle with olive oil. Season with a bit of sea salt and place in a 400˚F oven until slightly browned and tender.
While the cauliflower is roasting, peel, chop and boil a potato. When the potato is tender, drain the water and add to a blender. Then, chop a large onion and saute in a bit of olive oil. To prevent bitterness, don't let the onions brown. Remove them from the heat when they're just translucent.
Add the cauliflower and onions to the blender and blitz on low. Slowly add water until the ingredients are suspended and able to blend. Then, ultra-puree the mixture until smooth. Season with salt and serve hot, garnished with black sesame seeds and parsley.
I wanted something crunchy to go with the soup. I used rings of sweet onions and battered them with blended flax meal and xanthan gum. Then, I covered them with a breading of cornmeal and cornflour (starch), seasoned with a bit of onion powder and sea salt.