green bean casserole

1. For the Topping: Pulse bread, butter, salt and pepper in a food processor until mixture resembles coarse crumbs, about ten 1-second pulses. Transfer to a large bowl and toss with onions; set aside.

2. For the Beans and Sauce: Adjust oven rack to middle position and heat oven to 425°. Fill large bowl with ice water. Bring 4 quarts water to boil in a large Dutch oven. Add 2 Tbs salt and beans. Cook beans until bright green and crisp-tender, about 6 minutes. Drain beans into colander and plunge immediately into ice water to stop cooking. Spread beans on paper-towel-lined baking sheet to drain.

3. Add butter to now-empty Dutch oven and melt over medium-high heat until foaming subsides. Add mushrooms, garlic, ¾ tsp salt and ⅛ tsp pepper; cook until mushrooms release moisture and liquid evaporates, about 6 minutes. Add flour and cook for 1 minute, stirring constantly. Stir in broth and bring to simmer, stirring constantly. Add cream, reduce heat to medium, and simmer until sauce is thickened and reduced to 3½ cups, about 12 minutes. Season with salt and pepper to taste.

4. Add green beans to sauce and stir until evenly coated. Arrange in even layer in 3-quart (or 13 by 9-inch) baking dish. Sprinkle with topping and bake until top is golden brown and sauce is bubbling around edge, about 15 minutes.

Serve immediately.