1

Preheat oven to 350°F. Coat a shallow 1 1/2-quart baking dish with cooking spray.

2

Put green beans in a steamer basket; set basket in a saucepan over 1 inch of boiling water. Cover tightly and steam green beans until crisp-tender, 4 minutes; drain and rinse well with cold water. Spread green beans on a large clean kitchen towel; pat dry. Transfer to prepared baking dish.

3

To make topping, finely chop 1 shallot. Thinly slice remaining 2 shallots; set aside. Heat oil in a large nonstick skillet over medium heat; add chopped shallot. Cook, stirring occasionally, until browned and tender, 4 minutes. Add bread crumbs; cook, stirring occasionally, until golden, 3 minutes. Transfer mixture to a large bowl; stir in thyme, 1/4 tsp salt and pepper. Set aside to cool; stir in pecorino.

4

To make sauce, in a microwavable measuring cup, microwave milk on High until hot, 3 minutes; remove and cover to keep warm. (Or heat milk in small saucepan over medium-high heat just until small bubbles appear around edge, about 5 minutes. Remove pan from heat; cover and keep hot).

5

Meanwhile, melt butter in same skillet over medium heat; add sliced shallots. Cook, stirring occasionally, until golden, 4 minutes. Add mushrooms; increase heat and cook, stirring occasionally, until tender, 5 minutes. Stir in flour; cook, stirring frequently, 1 minute. Add hot milk, stirring constantly, in slow, steady stream; bring to boil over medium heat, whisking constantly. Cook 1 minute; stir in remaining 1/2 tsp salt and nutmeg or cayenne.

6

Pour sauce over green beans; toss gently to coat. Sprinkle casserole evenly with bread crumb topping; bake until topping is golden and sauce is bubbling, 25–30 minutes.

7

Serving size: generous 3/4 cup