Heat the butter in a pan and sweat the onion without colouring for about 5 minutes. Add the cauliflower florets and leaves, potato, garlic and chilli if using and cook for a further five minutes until softened. Add the fish sauce and stock and bring to the boil. Simmer for about 20 minutes until the cauliflower is completely tender.
Liquidise in a blender, then return to the pan. Pour in the coconut milk, season and reheat. Serve with lime wedges.
Freezing and defrosting guidelines
In order to enjoy optimum flavour and quality, frozen items are best used within 3 months of their freezing date. Always defrost and heat thoroughly before eating. For more tips on freezing and defrosting food, read our article Love Your Freezer.