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Classic Vegetarian Green Bean Casserole

Classic Vegetarian Green Bean Casserole features tender green beans baked in a creamy mushroom sauce and topped with crispy fried onions. The combination of savory mushrooms, garlic, and a smooth, seasoned sauce makes this traditional side dish a comforting addition to any meal.
Made with fresh green beans, vegetable broth, and simple pantry ingredients, this homemade green bean casserole delivers classic flavor without relying on condensed soup. It is an excellent choice for Thanksgiving dinner, holiday gatherings, or Sunday meals when a warm vegetable side belongs on the table.
Print Recipe
Prep Time 15 minutes
Cook Time 30 minutes
Total Time 45 minutes
Course Side Dish
Cuisine American
Servings 6 servings
Calories 240 kcal

Equipment

  • Large pot
  • Colander
  • Large skillet
  • Whisk or wooden spoon
  • 2-quart casserole dish
  • Measuring cups and spoons
  • Cutting board and knife

Ingredients
  

  • 1 1/2 pounds fresh green beans trimmed and cut into 2-inch pieces
  • 3 tablespoons unsalted butter
  • 10 ounces cremini or button mushrooms sliced
  • 2 garlic cloves minced
  • 3 tablespoons all-purpose flour
  • 1 1/2 cups low-sodium vegetable broth
  • 1 cup whole milk
  • 1 teaspoon soy sauce
  • 1/2 teaspoon salt or to taste
  • 1/4 teaspoon freshly ground black pepper
  • 1/4 teaspoon ground nutmeg
  • 1 1/2 cups crispy fried onions divided

Instructions
 

  • Prepare the oven and green beans. Preheat the oven to 375°F (190°C). Bring a large pot of salted water to a boil. Add the green beans and cook for 4 to 5 minutes, until bright green and just tender. Drain well and set aside.
  • Cook the mushrooms. Melt the butter in a large skillet over medium heat. Add the sliced mushrooms and cook for 6 to 8 minutes, stirring occasionally, until they release their moisture and begin to turn golden brown. Add the minced garlic and cook for another 30 seconds, until fragrant.
  • Make the creamy sauce. Sprinkle the flour over the mushrooms and stir until evenly coated. Cook for 1 to 2 minutes to remove the raw flour taste. Gradually whisk in the vegetable broth, followed by the milk, until the mixture is smooth. Add the soy sauce, salt, black pepper, and nutmeg.
  • Simmer until thickened. Cook the sauce over medium-low heat for 3 to 5 minutes, stirring frequently, until it thickens enough to coat the back of a spoon. Taste and adjust the seasoning as needed.
  • Combine the casserole. Add the drained green beans and 1 cup of the crispy fried onions to the skillet. Stir gently until the beans are evenly coated in the mushroom sauce. Transfer the mixture to a 2-quart casserole dish and spread it into an even layer.
  • Bake until bubbly. Place the casserole in the preheated oven and bake for 15 minutes, until the sauce is bubbling around the edges and the beans are heated through.
  • Add the crispy topping. Sprinkle the remaining 1/2 cup of fried onions evenly over the casserole. Return it to the oven for another 5 to 8 minutes, until the topping is golden and crisp.
  • Rest and serve. Let the casserole rest for about 5 minutes before serving. This allows the sauce to settle slightly while keeping the onion topping crisp.

Notes

  • Fresh or frozen green beans: Fresh green beans provide a slightly firmer texture. Frozen green beans can also be used; thaw and drain them thoroughly before adding them to the sauce.
  • Keep it vegetarian: Choose vegetable broth and check the ingredients on packaged fried onions to ensure they are suitable for a vegetarian diet.
  • Avoid a watery casserole: Drain the green beans well and allow the mushroom sauce to thicken before combining everything.
  • Make-ahead option: Prepare the green beans and mushroom sauce, combine them in the casserole dish, cover, and refrigerate for up to 24 hours. Add the crispy onion topping near the end of baking.
  • Storage: Refrigerate leftovers in an airtight container for up to 4 days. Reheat in a 350°F (175°C) oven until warmed through.
  • Crispy topping: Add the fried onions during the final minutes of baking rather than at the beginning to prevent them from becoming soggy.
  • Nutrition estimate: Values are approximate and depend on the brands of vegetable broth, milk, and crispy fried onions used.