In a large pot, heat the olive oil over medium heat. Add the chopped onion and sauté until translucent, about 5 minutes.
Stir in the minced garlic and cook for an additional minute until fragrant.
Add the cauliflower florets to the pot and pour in the vegetable broth. Bring to a boil, then reduce the heat and let it simmer for 15-20 minutes, or until the cauliflower is tender.
Remove the pot from heat and use an immersion blender to purée the soup until smooth. Alternatively, you can transfer the mixture in batches to a blender.
Return the puréed soup to the pot and stir in the heavy cream, salt, black pepper, and nutmeg. Heat gently until warmed through, but do not boil.
Serve hot, garnished with fresh chives or parsley.