Very Green Soup

Heat the oil until hot in a large soup pot or Dutch oven. Add the onion and sauté until translucent. Add the garlic and red pepper flakes and cook, while stirring, until fragrant, about 1 minute. Add the cauliflower and the chicken broth and bring to a boil, then reduce to a simmer. Simmer the cauliflower until tender, about 20 minutes. Once tender, stir in the baby spinach by large handfuls, waiting until the first batch has wilted down until you add the next. Season with hot sauce, salt, and pepper. Blend until velvety smooth in batches in a blender.