01 -
Preheat oven to 190°C (375°F).
02 -
Blanch green beans in boiling water for 3–4 minutes, then transfer to an ice bath. Drain and set aside.
03 -
In a large skillet, melt butter over medium heat. Sauté onion and garlic until soft, about 2–3 minutes.
04 -
Stir in flour and cook for 1 minute to form a roux. Slowly whisk in milk and broth. Cook, stirring constantly, until thickened (about 5 minutes).
05 -
Add salt, pepper, and nutmeg. Stir in cheese if using. Remove from heat.
06 -
Fold in green beans and mix until well coated. Transfer to a greased 9x13-inch baking dish.
07 -
Bake for 20 minutes. Remove from oven, sprinkle fried onions evenly on top, and return to oven for 5–10 more minutes until golden and bubbly.