Walnut and Garlic Sauce

The Ottomans were very fond of trees: it is said that the custom of planting poplars along the roadside, so familiar from driving in France, was adopted from an Ottoman tradition of providing marching armies with decent shade. They loved nut trees, too, and this recipe – for which hazelnuts can substitute for walnuts – is warm, earthy and fabulously versatile. Try it on the side with fish or chicken – or let it take centre stage as a pasta sauce.