Green Bean Casserole Makeover

Heat 2 teaspoons oil in a large nonstick skillet over medium-low heat.  Add onions and salt; cook, stirring often, until tender and light golden, 20 to 25 minutes. (Adjust heat as necessary and add a little water if onions brown too quickly.)  Transfer to a medium bowl and season with pepper.

Meanwhile, if using fresh green beans, steam or boil fresh green beans until crisp-tender, 5 to 7 minutes.  If using frozen, cook according to package directions.  Drain beans and refresh under cold running water.

Heat 2 teaspoons oil in skillet over medium-high heat.  Add mushrooms and cook, stirring or shaking pan from time to time, until browned and tender, 5 to 7 minutes.  Sprinkle flour over mushrooms and stir for a few seconds.  Add broth and bring to a boil, stirring constantly.  Simmer, stirring, until thickened, about 1 minute.  Remove from heat.

Stir in sour cream, soy sauce and pepper.  Stir in green beans.

Meanwhile, preheat oven to 400 degrees.  Coat an 8-by-11-inch (or similar 2-quart)  baking dish with cooking spray.  Spread green bean-mushroom mixture in a prepared baking dish.  

Top with caramelized onions.  Mix breadcrumbs and remaining 2 teaspoons oil in a small bowl; sprinkle over onions.  (Casserole can be prepared ahead.  Cover and refrigerate for up to 2 days.)

Bake casserole, uncovered, until heated through and topping is golden and crisp, 25 to 35 minutes.