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Easy Mushroom green bean casserole

Mushroom Green Bean Casserole

Make this classic mushroom green bean casserole from scratch with fresh ingredients. Perfect for holidays or family dinners with creamy sauce and crispy onions.
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Prep Time 25 minutes
Cook Time 1 hour
Total Time 1 hour 25 minutes
Course Dinner
Cuisine American
Servings 6 servings
Calories 320 kcal

Equipment

  • oven
  • large pot
  • Dutch oven or oven-safe skillet
  • cutting board
  • knife
  • measuring cups
  • measuring spoons
  • whisk
  • mixing bowl
  • 9x13-inch baking dish

Ingredients
  

Main Ingredients

  • 1.5 pounds fresh green beans trimmed
  • 4 tbsp unsalted butter
  • 1 pound cremini mushrooms sliced
  • 1 medium yellow onion finely chopped
  • 2 cloves garlic minced
  • 0.25 cup all-purpose flour
  • 2 cups low-sodium chicken or vegetable broth
  • 1 cup whole milk
  • 0.5 cup heavy cream
  • 1 tsp Dijon mustard
  • 1 tsp fresh thyme leaves chopped
  • 1 tsp kosher salt or to taste
  • 0.5 tsp freshly ground black pepper or to taste
  • 1 can crispy fried onions 2.8-ounce can, divided

Instructions
 

  • Preheat your oven to 375 degrees Fahrenheit. If using fresh green beans, bring a large pot of salted water to a rolling boil. Add the trimmed green beans and cook for 5 to 7 minutes, or until they are crisp-tender and vibrant green. Drain immediately and plunge them into an ice bath to stop the cooking, then drain thoroughly and set aside. If using frozen green beans, thaw them completely and pat them dry.
  • Melt the unsalted butter in a large Dutch oven or a deep, oven-safe skillet over medium-high heat. Add the sliced cremini mushrooms and cook, stirring occasionally, for 8 to 10 minutes, until they release their moisture, brown nicely, and are tender. Remove the mushrooms from the pan and set them aside.
  • Reduce the heat to medium. Add the finely chopped yellow onion to the same pan and cook, stirring frequently, for 5 to 7 minutes, until it softens and becomes translucent. Stir in the minced garlic and cook for another 1 minute, until fragrant, being careful not to let it brown.
  • Sprinkle the all-purpose flour over the onion and garlic mixture, stirring constantly for 1 minute to create a roux. Gradually whisk in the low-sodium chicken or vegetable broth, then the whole milk, and finally the heavy cream, ensuring there are no lumps. Bring the sauce to a gentle simmer, stirring constantly, and cook for 3 to 5 minutes, or until it has thickened enough to coat the back of a spoon. Stir in the Dijon mustard, chopped fresh thyme, kosher salt, and freshly ground black pepper. Taste and adjust seasonings as needed.
  • Return the cooked mushrooms and the prepared green beans to the sauce in the skillet or Dutch oven. Stir gently to ensure all the green beans are evenly coated. If your skillet is not oven-safe, transfer the mixture to a 9x13-inch baking dish.
  • Bake the casserole in the preheated oven for 20 to 25 minutes, or until the sauce is bubbly around the edges and the top is lightly golden.
  • Remove the casserole from the oven. Sprinkle 1 1/2 cups of the crispy fried onions evenly over the top. Return the casserole to the oven and bake for an additional 5 minutes, or until the crispy fried onions are golden brown and warmed through.
  • Let the casserole rest for 5 to 10 minutes before serving. This allows the sauce to set slightly, making it easier to serve.

Notes

Let the casserole rest for 5-10 minutes before serving to allow the sauce to set slightly.
Keyword casserole, green beans, holiday, mushrooms