Bring a large pot of salted water to a boil. Add the elbow macaroni and cook according to package instructions, usually about 7–8 minutes, until al dente. Drain the pasta and set aside.
In a mixing bowl, toss the shredded cooked chicken with the buffalo sauce until evenly coated. Set aside to let the flavors meld.
In a medium saucepan over medium heat, melt the butter. Once melted, whisk in the flour to create a roux. Continue whisking for about 2 minutes, allowing it to cook through but not brown. Gradually add the milk while whisking constantly to prevent lumps. Bring the mixture to a gentle simmer and cook until it thickens, about 3–5 minutes.
Stir in the garlic powder, onion powder, salt, and pepper. Gradually add the shredded cheddar cheese, stirring until melted and smooth.
Add the cooked macaroni and buffalo chicken to the cheese sauce, stirring gently to combine. If you want to incorporate a tangy punch, fold in the crumbled blue cheese at this stage.
You can serve the Buffalo Chicken Mac and Cheese immediately topped with chopped green onions, or transfer it to a baking dish and bake at 350°F (175°C) for 15–20 minutes until bubbly and golden on top. Baking adds a lovely contrast with a slightly crispy crust.