Skye Gyngell's Anchovy and Walnut Sauce

This anchovy and walnut sauce comes together quickly in a mortar and pestle, blending salty anchovies, fresh parsley, and garlic with the richness of walnuts. Once the solids are pounded to a smooth paste, a pour of oil brings it all together. It's designed to be spooned over lightly cooked green vegetables, adding a layer of flavor to broccoli, spinach, or chard.