Sweat the shallots in a little oil until translucent. Add the white chicken stock. Bring to the boil, add the potatoes and reduce to a simmer and cook.
In a large pan heat the sunflower oil until smoking, add the watercress, nettles and spinach stirring rapidly until wilted. Add the potato and stock and simmer for a further 4-6 minutes. Transfer to a blender and blend on full speed to a