Go Back
Green Bean Casserole with Crispy onions

Classic Thanksgiving Green Bean Casserole with Crispy Onions

Print Recipe Pin Recipe
Prep Time 30 minutes
Cook Time 40 minutes
Total Time 1 hour 10 minutes
Course Side Dish
Cuisine American
Servings 8

Equipment

  • Large Pot or Dutch Oven To blanch the green beans
  • Large skillet or sauté pan For cooking the mushroom sauce
  • Medium saucepan If frying your own onions
  • Slotted spoon or spider strainer For safe removal of fried onions
  • Mixing bowls For prepping onion topping
  • 9x13-inch baking dish To bake the casserole
  • Whisk To make the sauce smooth and lump-free
  • Colander or strainer To drain the green beans

Ingredients
  

For the Casserole Base

  • 1 ½ pounds fresh green beans trimmed and cut into 2-inch pieces
  • 3 tablespoons unsalted butter
  • 1 small yellow onion finely chopped
  • 2 garlic cloves minced
  • 8 ounces cremini mushrooms sliced
  • 3 tablespoons all-purpose flour
  • 1 cup chicken broth or vegetable broth for a vegetarian version
  • 1 cup half-and-half
  • 1 teaspoon kosher salt
  • ½ teaspoon freshly ground black pepper
  • ¼ teaspoon ground nutmeg optional but recommended

For the Crispy Onion Topping

  • 1 large yellow onion thinly sliced
  • ½ cup buttermilk
  • ½ cup all-purpose flour
  • ¼ cup cornstarch
  • ½ teaspoon paprika
  • Salt and pepper to taste
  • Vegetable oil for frying

Instructions
 

Blanch the Green Beans

  1. Start by bringing a large pot of salted water to a boil. Add the trimmed green beans and cook for 5-6 minutes until just tender but still vibrant green. Drain them immediately and transfer to a bowl of ice water to stop the cooking process. This keeps them crisp and fresh, unlike the soggy texture you might remember from older string bean casserole versions.

Make the Mushroom Cream Sauce

  1. In a large skillet over medium heat, melt the butter. Add the chopped onion and cook until softened, about 4 minutes. Stir in the garlic and cook for another minute. Add the sliced mushrooms and cook until they release their moisture and begin to brown—about 7-8 minutes.
  2. Sprinkle in the flour and stir constantly for about 1 minute to eliminate the raw flour taste. Slowly whisk in the broth, then the half-and-half. Add salt, pepper, and nutmeg. Simmer the sauce for 5-7 minutes until thickened and creamy.

Assemble the Casserole

  1. Preheat your oven to 375°F (190°C). In a large mixing bowl, combine the blanched green beans with the mushroom cream sauce. Mix until all the beans are coated evenly.
  2. Transfer the mixture to your baking dish and spread it out in an even layer. If you're using store-bought crispy onions, sprinkle them over the top now. If making your own, continue below.

Fry the Onion Topping

  1. Soak the sliced onions in buttermilk for 10 minutes. In a separate bowl, mix flour, cornstarch, paprika, salt, and pepper. Heat 1-2 inches of oil in a medium saucepan over medium-high heat. Toss the soaked onions in the flour mixture, shaking off excess, and fry in batches until golden brown and crisp—about 2-3 minutes per batch. Drain on paper towels and set aside.

Bake and Finish

  1. If using homemade fried onions, wait to add them. First, cover the casserole with foil and bake for 25 minutes. Remove foil, top with your fried onions, and return to the oven for an additional 10 minutes, until the top is golden and bubbling around the edges.
  2. Let the casserole rest for 5 minutes before serving.