Preheat oven to 425F.
Cook ziti according to package directions, drain, and set aside.
In a large sauce pan or dutch oven, heat olive oil over medium-high heat. Add in onions, carrots, and celery once hot and cook until just beginning to soften - about 5-6 minutes. Stir in garlic and cook another two minutes.
Add in ground chicken and cook until no longer pink, breaking up with wooden spoon and stirring occasionally.
Add in ricotta, buffalo sauce, and blue cheese dressing. Stir until all combined, then add in 1 cup of the mozzarella cheese. Stir.
Pour into 9 x 13 casserole dish and top with remaining mozzarella. Bake for 20 minutes.
Top with green onion and serve!