Mushroom Green Bean Casserole with Crispy Shallots

Makes 1 casserole · 1/6 of a casserole per serving

FOR SERVING

FOR THE CRISPY SHALLOTS

FOR THE CASSEROLE

Steps

1. Step 1

   Preheat the oven to 425°F (220°C) with a rack in the upper third. Line two rimmed baking sheets with parchment. Toss the green beans with the vegetable oil and salt on one sheet, and the sliced mushrooms with 1 Tbsp. of the remaining oil and a pinch of salt on the other. Roast the green beans until blistered in spots and just tender-crisp, 12–14 minutes; roast the mushrooms until deeply browned and their moisture has evaporated, 18–20 minutes, stirring once. Set both aside. (Roasting, not boiling, is what keeps the beans snappy and concentrates the mushrooms' flavor.)

   • 1 ½ lbfresh green beans, trimmed and halved
   • 1 tbspvegetable oil
   • ½ tspkosher salt
   • 1 lbcremini mushrooms, sliced 1/4-inch thick

2. Step 2

   While the vegetables roast, make the crispy shallots. Separate the shallot rings and toss them in a bowl with the flour and salt until evenly coated, shaking off excess. Heat the vegetable oil in a deep saucepan over medium-high until it reaches 325°F (163°C). Fry half the shallots, stirring gently, until pale gold, about 90 seconds. Lift out with a spider or slotted spoon onto a paper-towel-lined plate. Repeat with the remaining shallots. (First fry sets the coating; they crisp fully as they cool.)

   • 6 largeshallots, thinly sliced into rings
   • ½ cupall-purpose flour
   • ½ tspkosher salt
   • 2 cupsvegetable oil

3. Step 3

   Raise the oil heat to 375°F (190°C). Return the first batch of shallots to the oil and fry again until deep golden and shatter-crisp, 30–45 seconds. Drain on a fresh paper towel and sprinkle with a pinch of salt. Repeat with the second batch. Set aside. (The double fry is the difference between soggy and crisp.)

   • 6 largeshallots, thinly sliced into rings
   • ½ tspkosher salt

4. Step 4

   Reduce the oven to 375°F (190°C). In a large saucepan, melt the butter over medium heat. Add the flour and cook, whisking constantly, until the roux smells nutty and turns pale blond, 2–3 minutes. Whisk in the vegetable broth in a steady stream, then the heavy cream. Bring to a simmer and cook, whisking, until thickened enough to coat the back of a spoon, about 5 minutes.

   • 4 tbspunsalted butter
   • 3 tbspall-purpose flour
   • 1 ½ cupsvegetable broth
   • ½ cupheavy cream

5. Step 5

   Stir in the soy sauce, sherry vinegar, thyme, garlic, salt, and the black pepper. Add the roasted mushrooms and any pan juices, then the green beans, folding gently to coat. Taste and adjust: it should be savory, a little tangy, and well seasoned—add salt if flat, a few drops of vinegar if heavy, or a splash more soy if it needs depth.

   • 1 tbspsoy sauce
   • 1 tbspsherry vinegar
   • 1 tspfresh thyme leaves
   • 2 clovesgarlic, minced
   • ½ tspkosher salt
   • ½ tspblack pepper
   • 1 lbcremini mushrooms, sliced 1/4-inch thick
   • 1 ½ lbfresh green beans, trimmed and halved

6. Step 6

   Transfer the mixture to a 2-quart baking dish. Bake until bubbling at the edges and heated through, 20–25 minutes. If the top looks dry, tent loosely with foil. Scatter the crispy shallots over the top and bake 5 minutes more, just to warm them. (Don't add them earlier or they'll steam and lose their crunch.)

   • 6 largeshallots, thinly sliced into rings

7. Step 7

   Let the casserole rest 5 minutes before serving so the sauce sets. Serve hot, with extra crispy shallots on the side for those who want more crunch. Leftovers keep refrigerated up to 3 days; reheat covered at 350°F, and add fresh shallots before serving.

   • 6 largeshallots, thinly sliced into rings