# 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 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)
# Directions:
01 - Set oven temperature to 350°F.
02 - Bring a large pot of salted water to a boil. Add trimmed green beans and cook for 5 minutes until just tender yet still bright green. Drain in a colander and rinse under cold water to halt cooking.
03 - In a large skillet over medium heat, melt unsalted butter. Add sliced mushrooms and cook for 5 to 6 minutes until softened and browned. Incorporate the chopped onion and minced garlic, cooking 2 to 3 minutes until both are fully softened.
04 - Stir in all-purpose flour; cook for 1 minute, stirring constantly. Gradually whisk in milk, heavy cream, and vegetable broth. Simmer and cook until thickened, about 5 minutes. Season with salt, black pepper, and nutmeg if desired.
05 - Add drained green beans to the skillet and gently toss to coat evenly with the sauce.
06 - Transfer the mixture to a 2-quart baking dish. Sprinkle half the crispy fried onions over the top.
07 - Bake in preheated oven for 25 minutes until hot and bubbling.
08 - Remove from oven, add the remaining crispy fried onions on top, and bake for an additional 5 to 7 minutes until golden and crisp.
09 - Let the casserole cool for 5 minutes before serving.
