1. Preheat oven to 375°F and lightly grease a 9×13-inch baking dish.

2. Bring a large pot of salted water to a boil and cook 16 ounces elbow macaroni until just al dente. Drain and set aside.

3. In a large saucepan over medium heat, melt 4 tablespoons butter. Whisk in 4 tablespoons all-purpose flour and cook for about 1 minute until lightly golden.

4. Slowly whisk in 3 cups whole milk and 1 cup heavy cream. Cook, stirring constantly, until the mixture thickens and coats the back of a spoon.

5. Reduce heat to low and stir in 4 ounces softened cream cheese until fully melted.

6. Add 2 1/2 cups shredded sharp cheddar cheese and 1 cup shredded mozzarella cheese. Stir until smooth and creamy.

7. Mix in 1 cup sour cream, 1/2 teaspoon salt, 1/2 teaspoon black pepper, and 1 teaspoon garlic powder.

8. Fold in 6 slices of the cooked and crumbled bacon.

9. Add the drained macaroni to the cheese sauce and stir until evenly coated.

10. Transfer the mixture to the prepared baking dish. Sprinkle the remaining 1/2 cup sharp cheddar cheese and remaining 2 slices crumbled bacon over the top.

11. Bake for 20–25 minutes until bubbly and lightly golden.

12. Remove from oven and garnish with 1/4 cup sliced green onions before serving.