Heat the olive oil in a large saucepan over a medium heat, add the celery, garlic and potatoes and coat in the oil.

Add a splash of water and a big pinch of salt and cook, stirring regularly for 15 mins, adding a little more water if the veg begins to stick.

Pour in the vegetable stock and milk and simmer for 20 mins further, until the potatoes are falling apart and the celery is soft. Purée the soup with a stick blender.

Top with nigella seeds and serve with crusty bread.