This satisfying meal in a bowl is a riff on the Persian dish called soup-e jo. Though barley’s natural starch lends the soup body, béchamel, a mixture of butter, flour and milk, also is traditional for added richness and thickening. For ease, we skip the béchamel and instead simply mix a tablespoon of flour into the sautéed onion and mushrooms, then swirl in a little cream at the very end. Fragrant spices give the soup color and complexity, and fresh herbs (we like a combination of mint and dill, though just one type does nicely) lift and brighten the flavors.