Heat a large soup pot or dutch oven over medium-high heat. Add olive oil and onions and saute until the onions begin to soften, approximately 2-3 minutes. Add garlic and saute an additional minute.
Add vegetable broth, cauliflower florets, thyme, nutmeg, salt and pepper and bring to a boil. Reduce heat, cover and simmer over low heat until cauliflower is soft, approximately 20 minutes.
Turn heat off. Use an immersion blender and blend until cauliflower is smooth and creamy. Add ghee or butter, and salt and pepper, to taste. Garnish with dried parsley or chives, if desired.
If you do not have an immersion blender or prefer this method: allow the mixture to cool slightly and blend in a food processor or classic blender. You may have to do this in several batches. Be careful not to fill your blender more than halfway to avoid hot soup spills!