Place chicken in a pot of water and bring to a gentle boil. Cook for 15 minutes, until cooked through. Remove and use two forks to shred. Toss with blue cheese dressing and set aside.
Melt butter in a large high-walled skillet over medium heat. Add the onions and celery. Cook for 5 minutes, until softened. Add the garlic and cook for 1 more minute.
Add the undrained diced tomatoes and chicken broth. Bring to a boil and add the pasta. Submerge the pasta into the liquid and let it come back up to a boil.
Cover and let it boil for 10-13 minutes, or until al dente. Lift the lid and run a silicone spatula underneath the pasta a few times throughout cooking to ensure the pasta doesn't stick. Test a pasta noodle for doneness before proceeding.
Reduce heat to low. Add the buffalo sauce, cubed cream cheese, and shredded cheese. Use a silicone spatula to gently stir. The sauce will seem thin at first, but it continues to thicken as it stands.
Add the shredded chicken and red pepper flakes.
Optional: Once sauce is near your desired consistency, swirl in 2 Tablespoons COLD butter.
