Bring a large pot of salted water to a boil. Add elbow macaroni and cook until al dente, typically 7-9 minutes. Drain and set aside.

In a skillet over medium heat, melt 2 tablespoons of butter. Add cubed chicken breasts seasoned with salt and pepper, and sauté for 5-7 minutes until golden brown and cooked through.

In the same skillet, reduce heat and add another tablespoon of butter. Stir in 2 tablespoons of flour, whisking for 1-2 minutes until smooth. Gradually pour in 2 cups of milk, whisking until thickened for 4-5 minutes.

Lower heat and add 2 cups of shredded cheddar cheese to the sauce, stirring until melted and smooth.

Gently fold cooked elbow macaroni and sautéed chicken into the cheese sauce, coating everything well.

To bake, preheat the oven to 350°F (175°C). Transfer mixture to an oven-safe dish, sprinkle with breadcrumbs, and bake for about 20 minutes until golden and crispy.