Core cauliflower and cut into florets (approx. 6 cups) – reserve a few for garnish. In a large saucepan, heat butter and olive oil and sauté garlic and onion until softened. Add cauliflower, chicken stock, and rice. Bring to a boil, then reduce heat and simmer for 20 to 25 minutes until cauliflower is very tender. Remove from heat. Stir in lemon juice. Puree mixture in a food processor or blender, then return mixture to saucepan. Heat slowly, stir in milk, cayenne, nutmeg, and 2 T of the chives and cook, stirring constantly, until soup is hot. Cut off the outside of the Brie cheese if it is crusty and hard. Cut cheese into small chunks and add to soup, stirring until it slightly melted. Add salt and white pepper to taste.
To serve: While soup is heating, sauté reserved florets in 1 T of olive oil until slightly softened. Roll florets in Parmesan cheese and drop into soup. Sprinkle with reserved chives and paprika before serving.