# 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)
# Step-by-Step Guide:
01 - Preheat the oven to 350°F.
02 - Bring a large pot of salted water to a boil. Add green beans and cook for 5 minutes until just tender yet bright green. Drain and immediately rinse under cold water to halt cooking. Set aside.
03 - In a large skillet over medium heat, melt butter. Add mushrooms and cook for 5-6 minutes until tender and browned. Add onion and garlic, cooking an additional 2-3 minutes until softened.
04 - Stir in flour and cook for 1 minute, stirring constantly. Gradually whisk in milk, heavy cream, and vegetable broth. Bring to a simmer and cook for about 5 minutes until thickened. Season with salt, pepper, and nutmeg if desired.
05 - Add the drained green beans to the skillet and toss to evenly coat in the sauce.
06 - Transfer mixture to a 2-quart baking dish. Sprinkle half of the crispy fried onions evenly on top.
07 - Bake uncovered for 25 minutes until the casserole is bubbling.
08 - Remove from oven, top with remaining onions, then bake for an additional 5 to 7 minutes until golden and crisp.
09 - Allow to cool for 5 minutes before serving.
