Green Bean Dish With Onion Rings Top

• 1/2 cup 1% buttermilk
• 1/2 cup bread crumbs
• 1 onion, cut crosswise into 1/4"-thick slices and separated into rings
• 8 ounces mushrooms, sliced
• 1 small onion, chopped
• 1/2 teaspoon dried thyme
• 1/4 teaspoon salt
• 1/4 cup all-purpose flour
• 3 cups 1% milk
• 1 bag (16 ounces) frozen French-cut green beans, thawed and drained, or fresh garden/store green beans.

1. Preheat the oven to 500°F. Coat a medium baking dish and a baking sheet with cooking spray.
2. Place the buttermilk in a shallow bowl and the bread crumbs in another bowl. Dip the onion rings into the buttermilk, and then dredge in the bread crumbs. Place on the baking sheet. Coat with cooking spray. Bake for 20 minutes or until tender and golden brown.
3. Coat a medium saucepan with cooking spray and heat over medium heat. Add the mushrooms, onion, thyme, and salt. Cook, stirring occasionally, for 4 to 5 minutes or until the mushrooms give off their liquid. Sprinkle with the flour. Cook, stirring, for 1 minute. Add the milk. Cook, stirring constantly, for 3 to 4 minutes, or until thickened. Stir in the beans.
4. Reduce the oven temperature to 400°F. Pour the bean mixture into the prepared baking dish. Scatter the onion rings over the top. Bake for 25 to 30 minutes or until hot and bubbly.