Preheat the oven to 350°F (175°C).
In a large pot, bring salted water to a boil. Cook the elbow macaroni according to package instructions until al dente. Drain and set aside.
In a large skillet, melt the butter over medium heat. Once melted, whisk in the flour to create a roux, cooking for about 1-2 minutes until it’s slightly golden.
Gradually whisk in the milk, continuing to stir until the mixture thickens (about 3-5 minutes).
Add the garlic powder, onion powder, salt, and pepper. Stir in 1 ½ cups of the cheddar cheese until melted and creamy.
Mix the cooked macaroni, shredded chicken, and BBQ sauce into the cheese sauce, ensuring everything is thoroughly combined.
Transfer the mixture to a greased baking dish. Sprinkle the remaining ½ cup of cheddar cheese on top.
Bake in the preheated oven for 20 minutes or until the cheese is bubbly and slightly golden.
Remove from the oven and let it cool for a few minutes. Garnish with chopped green onions or parsley if desired.
Serve warm and enjoy your BBQ Chicken Mac and Cheese!