Spray 13x9-inch (3-quart) glass baking dish with cooking spray.
In 5-quart Dutch oven, melt butter over low heat.
Add onions and sugar; cook about 20 minutes, stirring occasionally, until onions are golden brown.
Add garlic and mushrooms; cook 5 to 10 minutes longer, stirring occasionally.
Add barley; cook 2 minutes.
Remove from heat; stir in bell pepper, parsley, soy sauce, sesame oil, pepper and thyme.
Pour into baking dish.
In microwavable bowl, microwave broth uncovered on High 4 minutes.
Pour broth over onion-mushroom mixture.
Cover with foil.
Bake 1 hour.
Let stand 10 minutes before serving.
Sprinkle with cheese.
Notes / Tips / Wine Advice:
Mushrooms add an earthy flavor to this dish. Feel free to use any variety of mushrooms, substituting them for the baby portabella mushrooms suggested in this recipe. Button mushrooms are readily available and offer a mild flavor, while wild mushrooms, such as enoki or shiitake, offer a richer flavor. In a taste panel, we thought this was reminiscent of the flavors of French Onion Soup, with the added meatiness of the mushrooms, in a delicious casserole.