📖 Instructions

1. Preheat your oven to 375°F (190°C). Grab a 9x13-inch baking dish and lightly grease it. Set it aside for now.
2. Prepare the Green Beans: If using fresh green beans, wash them thoroughly and trim the ends. You can leave them whole or snap them into 1-2 inch pieces, depending on your preference. Bring a large pot of salted water to a rolling boil. Add the trimmed green beans and blanch for 3-5 minutes, or until they are bright green and crisp-tender. They should still have a slight bite to them. Immediately drain the beans and plunge them into an ice bath to stop the cooking process and retain their vibrant color. Once cooled, drain again very well and set aside.
3. Sauté the Mushrooms: In a large, deep skillet or Dutch oven, melt 2 tablespoons of butter over medium heat. Add the sliced mushrooms (cremini or button work great). Cook, stirring occasionally, for 5-7 minutes until they are softened and have released their liquid. They should be beautifully browned. Remove the cooked mushrooms from the skillet and set them aside in a bowl.
4. Make the Roux: Add the remaining 4 tablespoons of butter to the same skillet over medium heat. Once melted, sprinkle in 1/4 cup of all-purpose flour. Whisk continuously for 1-2 minutes, creating a smooth paste. This is your roux, the base for our creamy sauce.
5. Build the Cream Sauce: Gradually pour in the 2 cups of chicken broth, whisking constantly to prevent lumps. Continue to whisk as the sauce thickens, about 2-3 minutes. Next, slowly add the 1 cup of heavy cream, still whisking. Bring the mixture to a gentle simmer, allowing it to thicken further. It should coat the back of a spoon.
6. Season and Combine: Stir in 1 teaspoon of garlic powder, 1/2 teaspoon of onion powder, 1/2 teaspoon of black pepper, and 1/4 teaspoon of salt (or to taste). Taste the sauce and adjust seasonings if needed. Return the sautéed mushrooms to the skillet. Gently fold in the blanched green beans, ensuring they are well coated with the creamy mushroom sauce. Don't be afraid to get in there with a spatula.
7. Transfer to Baking Dish: Pour the green bean and mushroom mixture into your prepared 9x13-inch baking dish, spreading it evenly. Give it a gentle shake to settle everything.
8. Add the Topping: In a medium bowl, combine 1.5 cups of crispy fried onions with 1 tablespoon of melted butter. Toss gently to coat the onions. Sprinkle this mixture evenly over the top of the green bean casserole. This buttery crispness is key!
9. Bake to Golden Perfection: Place the baking dish in your preheated oven. Bake for 20-25 minutes, or until the casserole is bubbling around the edges and the crispy fried onions on top are golden brown and perfectly crunchy. Keep an eye on the topping to prevent burning.
10. Rest and Serve: Carefully remove the casserole from the oven. Let it rest for 5-10 minutes before serving. This allows the sauce to set slightly, making it easier to serve. Dig in and enjoy your incredible homemade green bean casserole!