# Components:
→ 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 - Preheat oven to 350°F. Bring a large pot of salted water to a boil, add green beans and cook for 5 minutes until tender but still bright green. Drain and rinse under cold water to halt cooking. Set aside.
02 - In a large skillet over medium heat, melt butter. Add mushrooms and cook until tender and browned, about 5-6 minutes. Add onion and garlic, cooking an additional 2-3 minutes until softened.
03 - Sprinkle flour over vegetables and cook for 1 minute, stirring constantly. Gradually whisk in milk, cream, and vegetable broth. Simmer for 5 minutes until thickened. Season with salt, pepper, and optional nutmeg.
04 - Add drained green beans to skillet and toss until evenly coated with sauce.
05 - Transfer mixture to a 2-quart baking dish. Evenly sprinkle half of the crispy fried onions over the top.
06 - Bake uncovered for 25 minutes until bubbling.
07 - Remove from oven, top with remaining fried onions, and bake 5-7 minutes more until golden and crisp.
08 - Allow casserole to cool for 5 minutes before serving.
