Green Bean Casserole with Caramelized Onions

What Thanksgiving table would be complete without this iconic dish? Our version of this holiday classic uses only fresh ingredients and is topped with loads of sweet, caramelized onions. If you've never made your own green bean casserole from scratch, you've got to give this a try!

PREP TIME: 30 minutes
COOK TIME: 1 hours 0 minutes

Ingredients
1 clove garlic, finely chopped
6 black peppercorns
1 bay leaf
Pinch grated nutmeg
1 small onion, finely chopped (for the green bean mixture)
1 large onion, thinly sliced (for the onion topping)
3 cups white mushrooms, trimmed and sliced
2 teaspoons olive oil, divided
2 teaspoons butter
1/2 cup fresh breadcrumbs
2 cups whole milk
1/4 cup all-purpose flour
1/4 cup sour cream
1 teaspoon salt
1/2 teaspoon freshly ground pepper
2 cups fresh green beans, tough ends cut off, blanched*

Directions
Preheat oven to 350 degrees Fahrenheit. Spread breadcrumbs on a baking sheet and toast, stirring once, until lightly browned, 5 to 10 minutes. Set aside.

Make the onion topping: Heat 1 teaspoon oil and butter in a large nonstick skillet over low heat. Add sliced onion and cook, stirring occasionally, until very tender and golden, about 30 minutes. Set aside.

Make the sauce: Combine milk, peppercorns, bay leaf and nutmeg in a medium saucepan and heat over low until steaming. Remove from heat, let stand for 5 minutes and strain into a measuring cup. Discard peppercorns and bay leaf.

Heat 1 teaspoon oil in a large saucepan over medium heat. Add finely chopped onion and cook, stirring often, until golden, 3 to 4 minutes. Add mushrooms and garlic and cook, stirring, until tender, 3 to 4 minutes. Sprinkle flour over the vegetables and cook, stirring, for 1 minute. Slowly pour in the milk, whisking constantly. Bring to a boil, stirring. Reduce heat to low and cook, stirring, until thickened, about 1 minute. Remove from heat. Whisk in sour cream, salt and pepper.

To assemble and bake the casserole: Preheat oven to 425 degrees Fahrenheit. Spread green beans evenly over the bottom of a shallow 2-quart baking dish and pour the sauce over the top. Toss together the reserved onions and breadcrumbs in a small bowl and spread over the beans. Bake until bubbling, 15 to 25 minutes. Serve immediately.

*To blanch the green beans, bring a pot of water to a boil. Drop in green beans for 3 minutes and remove from water. Immerse right away in ice water to stop the cooking process. This will also help the beans retain their bright color. Once the beans are completely cooled, drain and set aside.