# What You'll Need:
→ Vegetables
01 - 2 lb fresh green beans, trimmed and cut into 2-inch pieces (or 2 lb frozen cut green beans, thawed and drained)
→ Sauce Base
02 - 2 tbsp unsalted butter
03 - 9 oz cremini or button mushrooms, sliced
04 - 1 small yellow onion, finely chopped
05 - 2 garlic cloves, minced
06 - 2 tbsp all-purpose flour
07 - 1 cup whole milk
08 - ½ cup heavy cream
09 - ½ cup low-sodium vegetable broth
10 - 1 tsp salt
11 - ½ tsp black pepper
12 - ½ tsp ground nutmeg (optional)
→ Topping
13 - 1½ cups crispy fried onions (store-bought or homemade)
# Method:
01 - Set oven temperature to 350°F.
02 - Bring a large pot of salted water to a boil, add green beans and cook for 5 minutes until tender yet crisp. Drain and rinse under cold water to halt cooking. Set aside.
03 - Melt butter in a large skillet over medium heat. Add mushrooms and cook 5-6 minutes until browned. Add onion and garlic, cooking for an additional 2-3 minutes until softened.
04 - Sprinkle flour into skillet and cook for 1 minute, stirring constantly. Gradually whisk in milk, cream, and vegetable broth. Simmer until sauce thickens, about 5 minutes. Season with salt, pepper, and nutmeg if using.
05 - Add green beans to skillet and toss gently to coat thoroughly with the sauce.
06 - Transfer mixture into a 2-quart baking dish. Sprinkle half of the crispy fried onions over the top.
07 - Bake uncovered for 25 minutes until bubbling around edges.
08 - Remove casserole from oven, evenly distribute remaining fried onions, and bake an additional 5-7 minutes until topping is golden and crisp.
09 - Allow casserole to rest for 5 minutes to set before serving.
