01 -
Preheat oven to 175°C (350°F). Spray a 13x9-inch baking dish with cooking spray; set aside.
02 -
Cook the macaroni in salted water per the package directions until al dente. Drain well and set aside.
03 -
Mix the shredded cheddar and pepper jack cheeses together. Set aside.
04 -
Melt butter in a 6-quart Dutch oven or heavy-bottomed pot over medium heat. Add celery and green onions (reserve some for garnishing). Cook for 2 minutes or until slightly softened.
05 -
Whisk flour, garlic salt, and black pepper into the butter mixture. Cook, stirring constantly, for 1 minute.
06 -
Gradually whisk in the milk. Increase heat to medium-high and bring to a gentle boil while stirring constantly. Reduce the heat to low and let the sauce simmer, uncovered, for 3–5 minutes, stirring occasionally to prevent sticking.
07 -
Stir in the buffalo sauce, cream cheese, ranch seasoning, and 2 cups of the shredded cheese mixture. Stir until the cheese is melted and the sauce is smooth. Remove from heat.
08 -
Add the cooked macaroni, chopped chicken, and bleu cheese crumbles to the pot with the cheese sauce. Stir gently until well combined.
09 -
Pour half of the macaroni mixture into the prepared baking dish. Sprinkle with 1 cup of the shredded cheese mixture. Repeat with the remaining macaroni mixture and top with the final cup of shredded cheese. Dot the top with 2 tablespoons of butter.
10 -
Bake, uncovered, for 35–45 minutes or until the top is golden and bubbling around the edges.
11 -
Let stand for 5 minutes before serving. Garnish with additional buffalo sauce, ranch dressing, bleu cheese crumbles, and reserved green onions.