Preheat your oven to 375°F (190°C) and grease a 9x13-inch baking dish.

Bring a large pot of salted water to a rolling boil, add the macaroni, and cook until al dente. Drain and rinse with cold water.

In a medium saucepan, melt butter, whisk in flour to create a roux, then gradually add milk until thickened. Stir in cheddar and cream cheese until melted.

In a large bowl, combine the drained macaroni, diced BBQ chicken, and cheese sauce. Fold together until macaroni is coated.

Pour the mixture into the prepared baking dish and spread evenly. Sprinkle extra cheese or breadcrumbs on top if desired.

Bake for about 25 minutes until bubbly and golden brown. Check towards the end to avoid burning.

Let rest for 5 minutes before serving. Garnish with sliced green onions.