Quick Recipe Version (TL;DR)
Quick Ingredients
- 2 lb (907 g) green beans, trimmed and halved
- 4 large shallots (about 12 oz/340 g), thinly sliced into rings
- 1/3 cup (40 g) all-purpose flour + 1/3 cup (40 g) cornstarch
- 2–3 cups (475–710 ml) neutral oil, for frying
- 1 lb (454 g) cremini mushrooms, sliced
- 3 tbsp (42 g) unsalted butter for sautéing + 4 tbsp (56 g) for sauce
- 1 tbsp (15 ml) olive oil
- 4 garlic cloves, minced
- 2 tsp fresh thyme leaves, chopped (or 1 tsp dried)
- 1.5 cups (360 ml) low-sodium chicken or vegetable broth
- 1.25 cups (300 ml) heavy cream
- 1/3 cup (30 g) finely grated Parmesan
- 1/2 tsp Dijon mustard (optional), pinch nutmeg
- Kosher salt and black pepper, lemon juice (1 tsp) to finish
Do This
- 1. Heat oven to 375°F (190°C). Boil a large pot of salted water and set up an ice bath.
- 2. Blanch beans 3–4 minutes; shock in ice bath, drain, and pat very dry.
- 3. Toss shallots with flour + cornstarch; fry at 325°F (165°C) in batches until golden. Salt and set aside.
- 4. Brown mushrooms in butter and olive oil over medium-high heat; season and set aside.
- 5. Make sauce: butter + garlic + thyme, stir in flour; whisk in wine (optional), broth, then cream. Simmer to thicken; add Parmesan, Dijon, nutmeg, salt, pepper, lemon.
- 6. Combine beans, mushrooms, and sauce in a greased 9×13-in (3-qt) dish; bake 20–25 min until bubbling.
- 7. Top with a mountain of crispy shallots and serve hot.
Why You’ll Love This Recipe
- Pure from-scratch flavor: no canned soup, just silky thyme-garlic cream.
- Golden, ultra-crispy fried shallots that stay crunchy on top.
- Blanched beans and well-browned mushrooms keep the casserole bright and hearty, not mushy.
- Holiday-worthy but weeknight-manageable, with make-ahead options.
Grocery List
- Produce: Green beans, shallots, cremini mushrooms, garlic, fresh thyme, lemon
- Dairy: Unsalted butter, heavy cream, Parmesan cheese
- Pantry: All-purpose flour, cornstarch, olive oil, neutral frying oil, low-sodium broth, Dijon mustard, nutmeg, kosher salt, black pepper, optional dry white wine
Full Ingredients
Crispy Fried Shallot Topping
- 4 large shallots (about 12 oz/340 g), peeled and thinly sliced into rings
- 1/3 cup (40 g) all-purpose flour
- 1/3 cup (40 g) cornstarch
- 3/4 tsp kosher salt, plus more to finish
- 2–3 cups (475–710 ml) neutral oil for frying (vegetable, canola, or peanut)
Green Beans & Mushrooms
- 2 lb (907 g) green beans, trimmed and halved
- 2 tbsp kosher salt for blanching water
- 1 lb (454 g) cremini mushrooms, sliced 1/4 inch (6 mm) thick
- 2 tbsp (28 g) unsalted butter
- 1 tbsp (15 ml) olive oil
- 1/2 tsp kosher salt and 1/2 tsp black pepper (for mushrooms)
Thyme-Garlic Cream Sauce
- 4 tbsp (56 g) unsalted butter
- 4 garlic cloves, minced
- 2 tsp fresh thyme leaves, chopped (or 1 tsp dried thyme)
- 4 tbsp (30 g) all-purpose flour
- 1/4 cup (60 ml) dry white wine (optional)
- 1.5 cups (360 ml) low-sodium chicken or vegetable broth
- 1.25 cups (300 ml) heavy cream
- 1/3 cup (30 g) finely grated Parmesan cheese
- 1/2 tsp Dijon mustard (optional)
- 1/8 tsp freshly grated nutmeg
- 1–1 1/4 tsp kosher salt and 1/2 tsp black pepper, or to taste
- 1 tsp (5 ml) fresh lemon juice, to finish
- Butter or oil, for greasing the baking dish
Step-by-Step Instructions
Step 1: Heat the oven and set up for success
Position a rack in the center of the oven and heat to 375°F (190°C). Lightly grease a 9×13-inch (3-quart) baking dish. Bring a large pot of water to a boil and season with 2 tbsp kosher salt for blanching the beans. Set a large bowl of ice water nearby. Pour 2–3 cups neutral oil into a Dutch oven or deep skillet and heat to 325°F (165°C) for the shallots.
Step 2: Blanch and shock the green beans
Add the green beans to the boiling water and cook until crisp-tender and bright green, 3–4 minutes. Immediately transfer to the ice bath to stop the cooking, then drain well and pat very dry with clean towels. Dry beans mean a creamier, thicker casserole.
Step 3: Fry the crispy shallots
In a bowl, toss the sliced shallots with the flour, cornstarch, and 3/4 tsp kosher salt until every ring is lightly coated. Working in batches, fry at 325°F (165°C), stirring gently, until golden and crisp, 3–4 minutes per batch. Transfer to a paper towel–lined rack and sprinkle with a little more salt while hot. Keep them uncovered so they stay crunchy.
Step 4: Brown the mushrooms
In a large skillet over medium-high heat, melt 2 tbsp butter with 1 tbsp olive oil. Add the mushrooms in an even layer (cook in two batches if needed) and leave them undisturbed for 3–4 minutes to sear. Stir and continue cooking until deeply browned and their moisture has evaporated, 6–8 minutes total. Season with 1/2 tsp kosher salt and 1/2 tsp black pepper. Transfer to a plate.
Step 5: Make the thyme-garlic cream sauce
Reduce the heat to medium. In the same skillet, melt 4 tbsp butter. Add garlic and thyme; cook just until fragrant, 30–60 seconds. Sprinkle in the flour and whisk for 2 minutes to form a pale roux. If using, whisk in the wine and let it bubble for 30 seconds. Gradually whisk in the broth, then the cream. Simmer, whisking often, until thick enough to coat the back of a spoon, 5–7 minutes. Off heat, stir in Parmesan, Dijon (if using), nutmeg, 1–1 1/4 tsp kosher salt, 1/2 tsp pepper, and lemon juice. Taste and adjust seasoning; the sauce should be well-seasoned.
Step 6: Combine and bake
Fold the blanched green beans and browned mushrooms into the hot sauce. Transfer to the prepared baking dish and spread evenly. Bake at 375°F (190°C) until bubbling around the edges and lightly browned on top, 20–25 minutes. If your dish is very full, set it on a rimmed baking sheet to catch drips.
Step 7: Finish with the crispy shallots and serve
Let the casserole rest for 10 minutes so it sets slightly. Mound the crispy fried shallots generously over the top just before serving. For extra crunch, you can briefly broil for 30–60 seconds, watching closely. Garnish with a few fresh thyme leaves if you like and serve hot.
Pro Tips
- Slice shallots uniformly thin for even frying; shake off excess flour to prevent clumping.
- Keep frying oil at 325°F (165°C). Too hot and the shallots darken before crisping; too cool and they absorb oil.
- Pat beans very dry after blanching—water thins the sauce.
- Brown mushrooms in batches without crowding so they sear instead of steam.
- The sauce should be nappe-thick (coats a spoon). If too thick, whisk in a splash of warm broth; if thin, simmer 1–2 minutes more.
Variations
- Gluten-Free: Use a 1:1 gluten-free flour blend (or rice flour) for the roux and only cornstarch for the shallot dredge.
- Vegan/Dairy-Free: Use olive oil or vegan butter, vegetable broth, and cashew cream or oat cream; skip Parmesan or use a vegan alternative and add 1–2 tbsp nutritional yeast.
- Bacon & Gruyère: Fold in 6 oz (170 g) crisp bacon bits with the mushrooms and swap Parmesan for 1/2 cup (50 g) shredded Gruyère.
Storage & Make-Ahead
Fried shallots can be made up to 2 days ahead: cool completely and store in an airtight container at room temperature with a paper towel; re-crisp on a sheet pan at 350°F (175°C) for 3–5 minutes if needed. Assemble the casserole (beans, mushrooms, sauce) up to 24 hours in advance, cover and refrigerate; bake 30–35 minutes from cold until hot and bubbling, then top with shallots. Leftovers keep 3–4 days refrigerated; reheat at 350°F (175°C) covered until hot, topping with fresh or re-crisped shallots. Freezing isn’t ideal for cream sauces, but you can freeze the sauced beans (without shallots) up to 1 month; thaw overnight and reheat gently, then add fresh shallots.
Nutrition (per serving)
Approximate: 360 calories; 27 g fat; 30 g carbohydrates; 8 g protein; 5 g fiber; 520 mg sodium. Values will vary based on brands and oil absorption.
