GREEN BEAN AND MUSHROOM CASSEROLE WITH CRISPY FRIED ONIONS

Steps:

• Make the casserole:
• Preheat oven to 425ºF. Line 2 rimmed baking sheets with parchment paper. Arrange mushrooms and 2 thyme sprigs in a single layer on prepared baking sheets. Drizzle with oil; season with 3/4 tsp. salt and 1/2 tsp. pepper. Roast mushrooms, stirring once and rotating pan halfway through, until lightly golden, crisp-tender, and liquid is evaporated (watch carefully as cook time can vary between types of mushrooms), 25-35 minutes. Remove sheets from oven and reduce oven temperature to 375ºF.
• Meanwhile, cook green beans in a large pot of boiling generously salted water until crisp-tender, 3-5 minutes. Drain in a colander and rinse under cold water to stop cooking. Drain well, then layer on a rimmed baking sheet with paper towels and pat dry. Wipe pot dry.
• Melt butter over medium-low heat in same pot. Add onion and garlic and cook, stirring occasionally, until tender, 5-8 minutes. Stir in flour and cook, stirring occasionally, until aroma is mildly nutty, 4-6 minutes. Add 3 Tbsp. cream and stir well to combine. Repeat twice, then stir in remaining cream, broth, bay leaves, and remaining 2 thyme sprigs. Bring to a simmer and cook, stirring occasionally and scraping sides of pot, until sauce is the consistency of slightly thickened cream and coats the back of a wooden spoon, about 20 minutes (do not over-reduce). Discard thyme and bay leaves. Stir in zest, 1/2 tsp. salt, and 1/4 tsp. pepper.
• Arrange beans and mushrooms in 3-qt. baking dish. Pour cream sauce over; stir to evenly coat. Bake casserole until sauce is thickened and bubbling around the edges, about 20 minutes.
• Make the fried onion topping:
• Pour oil into a large wide pot or high-sided skillet to a depth of 1/2". Heat over medium-high until hot but not smoking (about 350°F on a deep-fry thermometer). Line a rimmed baking sheet with paper towels.
• Whisk cornmeal, cornstarch, paprika, coriander, and cumin in a large shallow bowl. Toss onion rings in cornstarch mixture to coat.
• Working in batches, fry onion rings, stirring and turning occasionally, until golden and crisp, 2-3 minutes. Using tongs or a slotted spoon, transfer to prepared sheet to drain. Season with salt and pepper while hot.
• Bake the casserole:
• Arrange beans and mushrooms in a 3-quart baking dish. Pour cream sauce over; stir to evenly coat. Bake at 375ºF until sauce is thickened and bubbling around edges, about 20 minutes.
• Top casserole with fried onions and serve warm.
• Do Ahead
• Onions can be fried 1 day ahead. Let cool. Arrange in a flat layer on a paper towel-lined rimmed baking sheet, cover loosely with foil, and store at room temperature.
• Green beans and mushrooms can be cooked 3 days ahead; keep chilled in separate airtight containers. Let come to room temperature before using.