One-Pan Green Bean Hamburger Casserole

Preheat oven to 350 degrees.
In a Dutch oven or oven-safe skillet, cook the ground beef over medium-high heat until no longer pink, breaking it apart as it cooks. Drain excess fat if needed, then transfer the beef to a bowl and set aside.
1 pound Ground Beef
In the same pan, melt butter over medium heat. Add the diced onions and sauté for about 3 minutes, until softened. Stir in the flour to create a paste and cook, stirring constantly, for one minute.
2 Tablespoon Butter, ¼ cup Flour, ½ Onion
Slowly whisk in the half & half and beef broth, making sure there are no lumps. Let the mixture simmer for about 7 minutes, or until the sauce thickens.
1 cup Half & Half, 1 cup Beef Broth
Stir in the garlic powder, onion powder, black pepper, and salt, mixing well to combine.
½ teaspoon Garlic Powder, ½ teaspoon Onion Powder, ½ teaspoon Black Pepper, ¾ teaspoon Salt
Add the cooked beef mixture, green beans, and sour cream to the sauce, stirring until everything is well coated. If you're not using an oven-safe skillet, transfer the mixture to a casserole dish.
2 cans Cut Green Beans, ¼ cup Sour Cream
Sprinkle the shredded cheddar and mozzarella cheese evenly over the top.
½ cup Shredded Cheddar Cheese, ½ cup Mozzarella Cheese
Finish by adding a layer of fried onion straws for extra crunch.
¾ cup Fried Onion Straws
Baked uncovered for 30 minutes. Let the casserole stand for 5 minutes before serving.