# Ingredient List:
→ Vegetables
01 - 2 lb fresh green beans, trimmed and cut into 2-inch pieces (or frozen, 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 - 1/2 cup heavy cream
09 - 1/2 cup low-sodium vegetable broth
10 - 1 tsp salt
11 - 1/2 tsp black pepper
12 - 1/2 tsp ground nutmeg (optional)
→ Topping
13 - 1 1/2 cups crispy fried onions (store-bought or homemade)
# Steps:
01 - Set oven temperature to 350°F.
02 - Boil salted water in a large pot. Cook green beans for 5 minutes until just tender and bright green. 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 tender and browned. Stir in onion and garlic; cook 2-3 minutes until softened.
04 - Sprinkle flour over vegetables and cook 1 minute, stirring constantly. Gradually whisk in milk, cream, and vegetable broth. Simmer until thickened, about 5 minutes. Season with salt, pepper, and nutmeg if using.
05 - Add drained green beans to skillet and toss to coat evenly with sauce.
06 - Transfer mixture to a 2-quart baking dish. Sprinkle half of the fried onions over the top.
07 - Bake in preheated oven for 25 minutes until bubbling.
08 - Remove from oven. Top with remaining fried onions and bake an additional 5-7 minutes until golden and crisp.
09 - Allow casserole to rest for 5 minutes before serving.
