Heat the butter in a large saucepan. Add the celery, leek, spring onions and potato. Stir and cover with a lid. Sweat for 10 minutes, stir occasionally.
Pour in the stock and cook for 15 – 25 minutes until the potato is soft.
Add the spinach and cook until wilted.
Blitz with a stick blender to your preferred consistency. Finish with single cream or crème fraîche
Simply reheat and serve with crusty bread, al fresco if the weather permits!