Mushroom Burgers with Barley

These are some of my favorite veggie burgers in this book, in large part because they have such a pure flavor—it really tastes like a mushroom barley soup! Originally, I called for only barley, but I have found in subsequent years that farro works equally well; and if you have leftover cooked grains on hand, any chewy, substantial ones will do. You’ll need about 1¼ cups (195 g). And any assortment of mushrooms works great. Because shiitakes have such a distinctive texture, chewier than butt