This cheesy green bean casserole is a classic side dish to serve alongside your holiday turkey or ham. Instead of using a canned condensed mushroom soup as the base, this recipe features a simple creamy mushroom base from scratch. It can be prepped in advance and baked just before serving.
Preheat oven to 350ºF. In a skillet over medium heat, add the butter, garlic and shallots. Cook until fragrant, about 2 minutes.
Add the mushrooms. Season with salt and pepper. Cook until the mushrooms have softened, about 10 minutes.
Whisk in the flour. Add the chicken stock and milk. Bring to a gentle simmer and cook until thickened, about 10 minutes.
Remove from heat. Whisk in the cheese, green beans and ½ cup crispy onions.
Transfer to a baking dish and bake for 15 minutes. Sprinkle the top with remaining crispy onions and bake for an additional 15 minutes.