Preheat the oven to 400F and grease a 9x13” pan with nonstick cooking spray. 

Bring a large pot of salted water to a boil. Cook the ziti to al dente according to the package directions (about 8 minutes). Reserve ½ cup of starchy cooking water and then drain the pasta and set it aside. 

In a large pot or dutch oven, add the olive oil and warm it over medium-high heat. 

Sprinkle the cubed chicken with kosher salt, ranch seasoning, and black pepper. Toss to evenly coat the chicken with the seasoning. 

Add the chicken to the pan and sear for 1-2 minutes per side, or just until the chicken is lightly browned– it won’t be fully cooked in the middle. That's okay! Remove the chicken to a plate and set it aside. 

Add the butter to the pan (still over medium-high heat) and allow it to melt. Next, add the flour and whisk until a roux forms. Cook the roux, whisking constantly, for 1 minute. 

Next, add the milk and buffalo sauce. Whisk until no lumps of roux remain. Bring the sauce to a simmer and cook until it has thickened just slightly and barely coats the back of a spoon. 

Reduce the heat to low and add 1 ½ cups of cheddar cheese and ½ cup of pepper jack cheese. Stir until the cheese has melted. 

Remove the pan from the heat and add the cooked pasta, cooked chicken, green onion, and blue cheese crumbles. Stir to combine. If the sauce becomes too thin, add a splash of the reserved pasta water and continue to stir– we want a really gooey, creamy sauce. 

Transfer the pasta mixture to the greased pan and top with the remaining cheddar and pepper jack cheese.

Bake for 15-18 minutes or until the cheese is melty and bubbling. Garnish with additional crumbled blue cheese and sliced green onion, and enjoy.