1. Start by boiling salted water in a large pot. Add the elbow macaroni and cook until al dente, about 7-8 minutes. Once cooked, drain the macaroni and set it aside.

2. In a large skillet, melt 2 tablespoons of butter over medium heat. Add the seasoned chicken breasts to the skillet and cook until it's no longer pink in the middle, typically around 5-7 minutes. Once cooked, remove the chicken from the skillet and set it aside to rest.

3. Using the same skillet, melt the remaining butter and stir in the flour until well combined. Gradually whisk in the whole milk, stirring constantly until the mixture thickens, which should take about 4-5 minutes.

4. Lower the heat to medium-low and gradually stir in the shredded cheddar cheese until it melts and the sauce becomes smooth.

5. Fold in the cooked macaroni and the pieces of chicken until everything is well-coated in the creamy sauce. Make sure to taste and adjust seasoning with salt and pepper as needed.

6. For an added crunch, transfer the mixture to an oven-safe dish, top with breadcrumbs, and bake in a preheated oven at 350°F (175°C) for about 20 minutes or until the top is golden brown.

7. Let it cool for a few minutes before serving. Enjoy your Creamy Chicken Mac and Cheese!