Can-Don't Green Bean Casserole

In an 8-inch skillet, heat oil until shimmering. Separate sliced shallots into rings; toss in a small bowl with cornstarch. Shake off excess in a fine-mesh strainer. Add about a quarter of the shallots to the pan; cook, tossing a bit, until lightly golden, about 4 minutes. Using a slotted spoon, transfer shallots to a paper towel-lined plate. Repeat with remaining shallots.

Bring a large saucepan of salted water to a boil; prepare an ice bath. Cook beans in water until just crisp-tender, 4 to 5 minutes. Transfer to ice bath; drain and pat dry.

Preheat oven to 375°. In an extra-large skillet, melt butter over medium-high heat. Add mushrooms. Cook, tossing occasionally, until mushrooms have released their liquid, about 5 minutes. Add chopped shallots and garlic; cook, stirring, 2 minutes. Add madeira; cook, stirring, until almost evaporated. Add flour; stir to coat mushrooms; cook 1 minute. Add about half of broth, scraping up bits from bottom of pan. Add remaining broth and cream; bring to a simmer. Cook until sauce has thickened slightly, about 5 minutes. Season with kosher salt, pepper and nutmeg. Add green beans; stir to coat.

Transfer mixture to a 3-quart baking dish (or you can bake in skillet, if oven-proof). Bake, uncovered, until bubbling around edges, about 25 minutes. Sprinkle shallots over casserole.