Green Bean Casserole Recipe

4.90 from 65 votes

Make green bean casserole from scratch with frozen green beans, homemade mushroom sauce, and crispy baked onions instead of canned soup.

Prep Time35

Cook Time25

Total Time1

Course: Side Dish

Cuisine: American

Diet: Vegetarian

Servings: servings

Author: Yumna Jawad

Ingredients

For the Baked Crispy Onion Topping:

1 large onion very thinly sliced (mandoline recommended)
¼ cup all-purpose flour
½ cup panko breadcrumbs
½ teaspoon salt
¼ teaspoon black pepper
2 tablespoons olive oil

For the Mushroom Sauce and Green Beans:

1 tablespoon olive oil
1 pound mushrooms sliced
1 large onion thinly sliced
3 garlic cloves minced
2 cups 2% milk
3 tablespoons cornstarch
2 tablespoons water
2 teaspoons soy sauce
½ teaspoon salt
½ teaspoon black pepper
2 pounds frozen cut green beans
Cooking spray

Instructions

Make the Baked Crispy Onions

Preheat the oven to 425°F. Line a large baking sheet with parchment paper.
In a large bowl, toss onions with flour, panko, salt, and pepper. Drizzle olive oil over the mixture and toss again until evenly coated.
Spread onions out in a single layer on the baking sheet and bake for 15–20 minutes, tossing halfway, until golden and crisp. Watch closely near the end to prevent burning.

Make the Mushroom Sauce

In a large skillet over medium-high heat, add olive oil and mushrooms. Cook until browned, softened and releasing liquid, about 10 minutes.
Reduce heat to medium, add the onion and garlic, and cook until onions are translucent, about 5 minutes more.
Add milk and bring to a low simmer. In a small bowl, stir together cornstarch and water, then add to the skillet. Stir frequently until thickened. Add the soy sauce, salt and pepper and stir again to combine.

Assemble and Bake

Place the frozen green beans in a 9x13 baking dish. Pour the mushroom mixture over the green beans and stir to coat. Top evenly with the baked crispy onions.
Bake until the casserole is bubbling and the topping is golden, 10–15 minutes. Serve warm.

Video

Notes

Note: This recipe was updated in September 2025 to use a homemade crispy onion topping instead of breadcrumbs (as shown in the recipe video).

My Top Tip: Bake the onions until they're fully crisp before adding them to the casserole. They soften slightly during the final bake, so starting with crispy onions gives the best texture.

Storage: Once your green bean casserole cools down to room temperature, transfer any leftovers to an airtight container or cover the baking dish tightly with foil or plastic wrap. Refrigerate it within 2 hours of baking. The casserole will last 3–4 days in the fridge. To reheat the casserole, warm individual portions in the microwave or place the whole dish in a 350°F oven until warmed through.

Freezing: Make sure to use a freezer-safe baking dish and, after cooling, wrap the dish in a few layers of foil to prevent freezer burn. It'll last 3 months in the freezer. Thaw the casserole overnight in the fridge before reheating.

Nutrition

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