Wisconsin Green Bean Casserole

5 tablespoons butter, divided
1/4 cup all-purpose flour
1 cup 2% milk
1/2 cup lager beer or chicken broth
1-1/2 cups shredded cheddar cheese
1/2 teaspoon salt
1/2 teaspoon Worcestershire sauce
1/8 teaspoon cayenne pepper
1/8 teaspoon smoked paprika
6 cups frozen cut green beans (about 24 ounces), thawed
1 tablespoon finely chopped onion
1/2 cup dry bread crumbs

Preheat oven to 350°. In a large saucepan, melt 4 tablespoons butter over medium heat. Stir in flour until smooth; gradually whisk in milk and beer. Bring to a boil, stirring constantly; cook and stir until thickened, 1-2 minutes. Stir in cheese, salt, Worcestershire sauce, cayenne and paprika until blended. Add green beans and onion; stir to combine.
Transfer to a greased 2-qt. baking dish. Melt remaining 1 tablespoon butter; stir into bread crumbs. Sprinkle over casserole. Bake, uncovered, until bubbly and top is golden brown, 30-35 minutes.