Preheat the oven to 350°F (175°C).
Cook the elbow macaroni according to package instructions until al dente. Drain and set aside.
In a large saucepan, melt 3 tablespoons of unsalted butter over medium heat.
Whisk in the all-purpose flour and cook for 1 to 2 minutes until the mixture is lightly golden and bubbly.
Slowly whisk in the whole milk, ensuring no lumps form. Continue to cook and whisk until the sauce thickens, about 5 to 7 minutes.
Remove the sauce from heat and stir in the shredded sharp cheddar cheese and mozzarella cheese until melted and smooth.
Add salt, black pepper, garlic powder, onion powder, and smoked paprika to the cheese sauce and stir to combine.
Add the cooked macaroni and shredded chicken to the cheese sauce and stir until everything is evenly coated.
Transfer the mac and cheese mixture into a greased 9×13 inch baking dish and spread evenly.
In a small bowl, combine the panko breadcrumbs with the melted butter and mix until the crumbs are evenly coated.
Sprinkle the buttered breadcrumbs evenly over the top of the casserole.
Bake in the preheated oven for 25 to 30 minutes, or until the top is golden brown and the casserole is bubbly.
Remove from the oven and let cool for 5 minutes before serving.