Bring a large pot of salted water to a rolling boil. Add the elbow macaroni and cook according to package directions until al dente, usually 7 to 8 minutes. Drain well and set aside.

While the pasta cooks, heat 2 tablespoons of butter in a large skillet over medium heat. Season the cubed chicken with salt and pepper, then add to the skillet in a single layer. Cook for 5 to 7 minutes, stirring occasionally, until golden brown and the internal temperature reaches 165°F. Remove from skillet and set aside.

In the same skillet, melt the remaining 2 tablespoons of butter over medium heat. Sprinkle in the flour and whisk constantly for about 1 minute to create a roux. The mixture should turn light golden and smell slightly nutty.

Slowly pour in the milk while whisking continuously to prevent lumps. Keep whisking for 4 to 5 minutes until the sauce thickens enough to coat the back of a spoon. Add the garlic powder and stir to combine.

Reduce heat to low and gradually add the shredded cheddar cheese, stirring constantly until completely melted and smooth. Never let the sauce boil once cheese is added. Gently fold in the cooked pasta and chicken, tossing until everything is evenly coated.

For a baked version, transfer the mixture to a greased 9x13 inch baking dish. Sprinkle panko breadcrumbs evenly over the top and bake at 350°F for 20 minutes until golden brown and crispy. Serve immediately.