Green Bean Casserole

Instructions

1. Preheat the oven to 375F. Begin by preparing the onion topping. Then make the mushroom sauce. While those are cooking, prepare the green beans.
2. For the onion topping: Peel and thinly slice onion. Grate parmesan. Heat half of the butter in a pan over medium heat. Add the onions and sauté until translucent and caramelized. Transfer the onions to a separate mixing bowl.
3. Add the remaining butter to the pan. When foaming, add in the breadcrumbs and stir until combined. Cook, stirring occasionally until they are toasted and lightly golden. Remove from heat and transfer to the bowl with the onions. Stir in the salt and parmesan, and toss the mixture until combined. Set aside.
4. For the mushroom sauce: Mince garlic. Thinly slice mushrooms, if desired. Grate parmesan. In the same pan, heat butter on medium high heat until foaming. Add mushrooms and sauté until they are soft. Add the garlic and saute for an additional 1-2 minutes. Sprinkle with flour, and stir, and sauté for an additional minute, stirring occasionally.
5. Slowly add chicken broth, whisking to combine until smooth. Whisk in milk, and bring the mixture to a simmer. Let cook for an additional minute until thickened, then stir in Parmesan cheese, salt, and pepper until the cheese is melted. Reduce heat to low until the sauce is ready to be tossed with the green beans. If too thick, add a bit more milk to thin.
6. For the beans: Bring a large stockpot of water to a boil. Add the green beans and boil for 3-5 minutes, or until they reach your desired level of doneness. Drain the green beans, then transfer them to the bowl of ice water to prevent overcooking more.
7. Transfer the green beans into the pan with the sauce and toss until combined.
8. Pour the green bean mixture into a baking dish. Sprinkle the onion topping evenly on top. Bake for 25 minutes and serve.