2 pounds fresh green beans, rinsed, trimmed and cut into 1-inch pieces
1 teaspoon kosher salt, divided (optional)
2 tablespoon olive oil
1 medium yellow onion, quartered and thinly sliced
1 pound fresh mushrooms, stemmed and sliced 1/4-inch thick
1 tablespoon fresh thyme leaves
1 1/2 teaspoons dry sherry (optional)
1/8 teaspoon freshly ground nutmeg
2 cups fat-free low-sodium vegetable broth
1/4 cup white whole wheat flour
1 1/2 cups plain lowfat Greek yogurt
2 tablespoon Dijon mustard
For the topping: Heat oven to 400°F and arrange a rack in the middle. Combine the onions, flour and kosher salt in a large mixing bowl and toss to combine. Brush a rimmed baking sheet with a thin layer of olive oil and evenly spread the onions on the pan.
Bake, stirring a few times, until golden brown, approximately 30 minutes. Remove from the oven and set aside until ready to use. (Can be made up to two days ahead and stored in an airtight container at room temperature.)
For the filling: Heat oven to 350°F and arrange a rack in the middle.
While the topping is roasting, prepare the beans. Bring a pot of water to a boil over high heat. Add 1/4 teaspoon of kosher salt and the beans and cook until bright green, about 2 minutes. Drain and immediately plunge the beans into a large bowl of ice water to stop the cooking. Drain and set aside.
Heat the oil in a large pan over medium-high heat. When it shimmers, stir in the onion and cook until just softened. Stir in the mushrooms, thyme, remaining kosher salt and some freshly ground black pepper and cook, stirring occasionally, until the mushrooms begin to give up some of their liquid, about 5 minutes.
Stir in the sherry, if using, and cook until alcohol smell is gone. Add nutmeg, sprinkle the flour over the mixture, stir to combine, and cook for 1 minute. Stir in the broth and simmer until just starting to thicken. Remove from heat, stir in the green beans, yogurt and mustard.
Turn mixture into a 2-to 3-quart baking dish, and sprinkle the top with the roasted onions. Bake until bubbly, approximately 15 minutes. Remove and serve warm. Makes 10 servings.
Nutritional information (per serving): 120 calories, 35 fat calories, 3.5 fat grams, 0 mg cholesterol, 18 carbs, 4 grams fiber, 7 grams sugar, 7 grams protein.