Heat olive oil in a large pot over medium high heat. Add the pancetta to flavour the oil; cook until golden, then remove and keep for garnish.
Stir in chopped onions, cauliflower, parsley, sage and rosemary. Cook, stirring frequently until the onion and cauliflower have browned, about 5 or 10 minutes. Stir in tomatoes and stock; bring to the boil. Lower heat and simmer until cauliflower is tender, about 15 to 20 minutes.
Add cream and puree the soup either with a hand held immersion blender or a food processor.
Serve with reserved pancetta, a drizzle of extra virgin olive oil and grated Parmesan cheese.