Potato Soup with Wilted Leaves

In a large, thick-based saucepan, gently melt 2 oz (50 g) of the butter, then add the potatoes and onions, stirring them all around with a wooden spoon so they get a nice coating of butter.

Season with salt and pepper, then cover and let the vegetables sweat over a very low heat for about 15 minutes, stirring everything now and then. After that, add the stock and milk, bring to simmering point, cover and let the soup simmer very gently for a further 20 minutes or until the potatoes are soft – be careful as, if you have the heat too high, the milk may cause it to boil over. Now allow the soup to cool a little, before putting the whole lot into a blender in batches and blend to a purée (a bowl to put each batch in is helpful here). Return the soup to the pan, then gently reheat it, tasting to check the seasoning.

Meanwhile, roughly chop the watercress, spinach and rocket (including the stalks) and stir them into the soup with the remaining 1 oz (25 g) butter. As soon as the leaves have wilted, serve the soup in warm bowls.