Begin by bringing a large pot of salted water to a boil. Add the elbow macaroni and cook until al dente, about 7-8 minutes. Drain and set aside.

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

In the same skillet, melt another 2 tablespoons of butter. Whisk in 2 tablespoons of flour until smooth and bubbly, about 1-2 minutes. Gradually add 2 cups of milk, whisking until the sauce thickens, about 4-5 minutes.

Lower the heat and stir in 2 cups of shredded cheddar cheese until completely melted and combined. The sauce should be velvety and smooth.

Add the cooked pasta and sautéed chicken into the cheese sauce, folding gently to coat evenly while keeping the heat low.

(Optional) Preheat oven to 350°F (175°C). Transfer the mixture to an oven-safe dish, sprinkle breadcrumbs on top, and bake for 20 minutes until golden brown and bubbly.

Remove from oven, let cool slightly, garnish with parsley, and serve warm.