1.Heat the oil in a large saucepan on medium. Saute the onion for 2-3 minutes, until tender.
2.Add cauliflower, potatoes and zucchini. Cook for 2 minutes, stirring. Add stock. Bring to the boil. Reduce heat and simmer for 20-25 minutes or until vegetables are tender. Stir in spinach leaves.
3.Using a hand blender or a food processor, process soup until smooth. Blend in cream. Reheat gently and season to taste. Serve soup topped with extra cream, prosciutto and crusty bread.
Prepare crispy prosciutto by cooking in a dry frying pan for 2-3 minutes, until crisp. Or arrange on an oven tray and bake in a moderate oven, 180°C for 5-10 minutes.