If using fresh spinach, you’ll need quite a lot of it (I normally use 2 bunches). Wash the spinach thoroughly to remove dirt before using. Bring a pot of water to the boil, and have a large bowl of cold water ready to plunge the spinach into to stop it cooking. When the water comes to the boil, add the spinach and allow to cook briefly – only until it turns bright green. Use tongs to remove the spinach and place straight into the bowl of cold water. Drain in a colander, then blend into a fine puree.