Sorrel-Flavored Mushroom Barley Soup

“A bread of affliction,” the Passover Haggadah calls it. And the first matzoh probably was. Made of barley flour like the Hebrew breads at that time, it was dense and tooth-defying. As the lighter, more delicate wheat flour became available, baked goods made of barley flour took on an air of poverty and deprivation, gradually losing favor among Jews.

Not so fluffy barley kernels. For soups and pilafs, where it offers a creamy, risotto-like richness, barley has remained a kitchen sta