Bring a large pot of salted water to a boil. Cook pasta according to package instructions to al dente. Reserve some of the pasta water just before draining.
Once pasta is finished cooking, drain and put back in the large pot on the stove on med-low heat. Add the butter, milk, and Velveeta. Sir until cheese is almost all melted. Stir in the other two cheeses, garlic powder, and salt and pepper to taste. Stir until melted. Stir in the buffalo chicken mixture. Make sure everything is hot and warmed through. You can always add more milk and/or reserved pasta water if more moisture is needed.
Lightly grease a medium baking dish, and pour the mac and cheese mixture into the dish. Sprinkle with breadcrumb mixture over the top. Place under the broiler for about 5 minutes or until golden brown. Watch it closely to avoid burning!
The garlic white cheddar and fontina cheeses are sold in block form in the specialty cheese area of the supermarket. Regular white cheddar is just fine too!
If you are not a spicy fan or buffalo fan you can omit the buffalo sauce all together and you still have a delicious mac and cheese dish. Chicken or no chicken, it's still great!
The 1/2 cup of buffalo sauce really only adds a hint of buffalo flavor, it's definitely not an overwhelming buffalo kick. Like it more spicy? Add more buffalo sauce or sriracha!