Bring a large pot of salted water to a boil. Add 8 ounces of elbow macaroni and cook according to package instructions (7–8 minutes) until al dente. Drain well and set aside.
In a medium saucepan, melt 1 tablespoon of butter over medium heat. Stir in 1/2 teaspoon garlic powder and 1/2 teaspoon onion powder. Slowly whisk in 1/2 cup of milk, heating until warm but not boiling. Gradually add 2 cups shredded cheddar cheese and 1 cup shredded mozzarella cheese, stirring constantly until melted and smooth.
In a large mixing bowl, toss 2 cups cooked, shredded chicken with 1 cup barbecue sauce until evenly coated.
Add the cooked macaroni to the bowl with the BBQ chicken. Pour the cheese sauce over the top and gently fold everything together until well combined. Season with salt and pepper to taste.
In a small pan, heat 2 tablespoons olive oil over medium heat. Add 1/2 cup breadcrumbs and stir frequently until golden brown and crispy, about 3–4 minutes.
Preheat your oven to 350°F (175°C). Transfer the mac and cheese mixture to a greased baking dish. Evenly sprinkle the toasted breadcrumbs on top. Bake uncovered for 20 minutes, or until the topping is golden and the dish is bubbly.
Let the dish cool for a few minutes before serving. Enjoy your BBQ Chicken Mac and Cheese!