Preheat oven to 400 degrees. Spray a 9 x 13 inch casserole dish with non-stick spray and set aside.
In a large bowl, whisk together the cream cheese, yogurt, milk, and hot sauce until smooth. Stir in the pasta, chicken, and half the cheese. Mix well and pour into the prepared casserole dish. Sprinkle the remaining cheese over top.
Bake for 15 to 20 minutes or until top is golden brown. Sprinkle with green onions and serve.