1.In a large pan, heat butter over medium and cook leeks, stirring frequently until collapsed but not coloured.
2.Add parsnips and chestnuts and continue cooking a further 5 minutes or until parsnips have softened. Stir in spinach and stock and season with salt and pepper.
3.Bring to the boil; reduce heat and simmer 20 minutes or until vegetables are cooked.
4.Puree until smooth and return to the heat; stir through creme fraiche and serve in large heated soup bowls with a grinding of black pepper and toasted garlic sourdough bread.