Q1: Is it really worth it to make the crispy onions from scratch?

Yes, a thousand times yes! While it is an extra step, the flavor and texture of homemade, buttermilk-soaked, and deep-fried onions are vastly superior to the canned variety. They are much lighter, crunchier, less greasy, and have a beautiful, sweet, and toasty onion flavor. They truly elevate this casserole from a simple side dish to a gourmet masterpiece.

Q2: What is the secret to a really flavorful, from-scratch mushroom sauce?

The secret is using a duo of mushrooms ! The fresh cremini mushrooms provide a classic, earthy flavor and a meaty texture. But the real game-changer is the addition of rehydrated dried shiitake mushrooms and their soaking liquid . Dried shiitakes have an incredibly deep, smoky, and savory umami flavor that adds a profound richness to the final sauce.

Q3: Can I make this entire casserole ahead of time for Thanksgiving?

Yes, this is the perfect make-ahead dish for a stress-free holiday! The best method is to prepare all the components separately and store them as directed in the "Make-Ahead Tips" section above. The final assembly and baking will only take about 35 minutes on the big day, and your onion topping will be perfectly crispy.

Q4: Can I bake my homemade onions instead of deep-frying them?

Yes, you can. For an easier, less messy method, you can bake them. After you have coated the buttermilk-soaked onions in the flour and panko, spread them in a single layer on a greased baking sheet. Bake them in a very hot oven, around 475°F , for about 30 minutes, tossing them a few times, until they are deep golden brown and crispy.

Q5: Why do you soak the onions in buttermilk first?

This is a classic Southern trick for fantastic fried onions! The buttermilk does two things. First, its gentle acidity helps to tenderize the onion slices and mellow out their sharp, pungent bite. Second, the thick buttermilk acts as a perfect "glue," helping the flour coating to adhere beautifully to the onions, which results in a thicker, crispier crust.

The Ultimate From-Scratch Green Bean Casserole (Best Ever!)

A from-scratch version of the classic American Green Bean Casserole, featuring homemade crispy fried onions and a rich, creamy mushroom sauce. The sauce is built with a combination of rehydrated shiitake and fresh cremini mushrooms, thickened with a roux and a mix of chicken (or vegetable) broth and heavy cream. Fresh green beans are blanched and then simmered in the sauce. The casserole is topped with onions that have been soaked in buttermilk, dredged in flour, and deep-fried until golden and crispy.

Author: Evelyn
Prep Time: 30 minutes
Cook Time: 1 hour
Total Time: 1 hour 30 minutes
Yield: 10-12 servings 1x
Category: Side Dish
Method: Sautéing, Simmering, Deep-Frying
Cuisine: American
Diet: Vegetarian

Ingredients

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For the Casserole:
1 ounce dried shiitake mushrooms
4 tablespoons unsalted butter
1 white onion, diced
12 ounces cremini mushrooms, sliced
6 tablespoons all-purpose flour
4 cups low-sodium chicken or vegetable broth
Kosher salt
1 1/2 pounds green beans, trimmed and halved
3/4 cup heavy cream
Freshly ground black pepper
For the Topping:
1 white onion, halved and thinly sliced
1 cup buttermilk
2 cups all-purpose flour
Vegetable oil, for frying

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Instructions

Prepare the Mushrooms and Sauce: Place the dried shiitake mushrooms in a small bowl, cover with about 2 cups of boiling water, and let steep for 20 minutes. Strain through a fine-mesh strainer, reserving 1/2 cup of the liquid. Slice the steeped mushrooms.
Melt the butter in a large Dutch oven over medium heat. Add the diced onion and cook for 7 to 10 minutes, until softened. Add the sliced cremini and shiitake mushrooms and sauté for 10 minutes, until softened and most of their liquid has evaporated.
Sprinkle in the flour and cook, stirring, for 1 minute. Add the broth and the reserved mushroom liquid. Bring to a boil, then reduce the heat and simmer for 5 to 10 minutes, until thickened.
Prepare the Green Beans: While the sauce simmers, bring a pot of salted water to a boil. Add the green beans and cook for 7 to 10 minutes, until crisp-tender. Drain well.
Add the drained green beans to the mushroom sauce. Cook, stirring, for 10 to 12 minutes until the beans are very tender and the sauce is thick. Stir in the heavy cream and season with 2 teaspoons of salt and pepper.
Make the Onion Topping: Soak the sliced onions in the buttermilk for 5 minutes. Combine 2 cups of flour and 1 teaspoon of salt in a medium bowl.
Heat 2 to 3 inches of vegetable oil in a large pot to 350°F. Working in batches, drain the onions, toss them in the flour mixture, shake off the excess, and fry for 4 to 6 minutes, until golden. Drain on paper towels.
Assemble: Transfer the green bean mixture to a 4-quart baking dish and top with the fried onions. Serve immediately, or follow make-ahead instructions.

Notes

This recipe is made completely from scratch, including the crispy onion topping, as an alternative to using canned condensed soup and onions.
Soaking the onions in buttermilk before frying helps them to become tender and flavorful.
The casserole can be made up to 2 hours ahead; refrigerate the casserole without the topping. Before serving, bring to room temperature, reheat at 350°F for 30 minutes, then add the onion topping and bake for 5 more minutes.

Nutrition

Serving Size: 1/10 of casserole
Calories: 300-380
Sugar: 8-12 g
Sodium: 700-900 mg
Fat: 20-28 g
Saturated Fat: 9-13 g
Trans Fat: 0 g
Carbohydrates: 25-30 g
Fiber: 4-6 g
Protein: 6-9 g
Cholesterol: 40-60 mg

Find it online: https://cookupjoy.com/green-bean-casserole/