# What You'll Need:
→ Vegetables
01 - 2 pounds fresh green beans, trimmed and cut into 2-inch pieces, or substitute with 2 pounds frozen cut green beans, thawed and drained
→ Sauce Base
02 - 2 tablespoons unsalted butter
03 - 9 ounces cremini or button mushrooms, sliced
04 - 1 small yellow onion, finely chopped
05 - 2 garlic cloves, minced
06 - 2 tablespoons all-purpose flour
07 - 1 cup whole milk
08 - 1/2 cup heavy cream
09 - 1/2 cup low-sodium vegetable broth
10 - 1 teaspoon salt
11 - 1/2 teaspoon black pepper
12 - 1/2 teaspoon ground nutmeg, optional
→ Topping
13 - 1 1/2 cups crispy fried onions, store-bought or homemade
# How to Make It:
01 - Set the oven to 350°F (180°C) and allow it to preheat.
02 - Bring a large pot of salted water to a boil. Add green beans and cook for 5 minutes until just tender but still bright green. Drain and rinse under cold water to stop further cooking. Set aside.
03 - In a large skillet over medium heat, melt the butter. Add sliced mushrooms and cook for 5 to 6 minutes until tender and lightly browned. Stir in the chopped onion and minced garlic, and cook for an additional 2 to 3 minutes until softened.
04 - Add flour and stir constantly for 1 minute. Gradually whisk in whole milk, heavy cream, and vegetable broth. Bring the mixture to a simmer and cook until thickened, about 5 minutes. Season with salt, black pepper, and nutmeg if desired.
05 - Add blanched green beans to the skillet. Toss to ensure all beans are evenly coated with the sauce.
06 - Transfer the mixture to a 2-quart baking dish. Sprinkle half of the crispy fried onions evenly over the top.
07 - Place the baking dish in the oven and bake for 25 minutes until the casserole is bubbling.
08 - Remove from the oven. Top with the remaining fried onions, and bake for 5 to 7 minutes more until golden and crisp.
09 - Allow the casserole to cool for 5 minutes before serving.
