Wholesome and nutty, barley is a superb alternative to arborio rice in this risotto, since it’s naturally plump and chewy when cooked. The grated Parmesan and butter stirred in at the end release the barley’s starches, creating a silky, creamy texture. Make sure to use pearl barley, not hulled, since it cooks much faster and is more tender. As for the mushrooms, white button, cremini and earthy shiitakes are a tasty, accessible mix, though any combination of oyster, king trumpet and maitake…