Preheat oven to 375°F (190°C) and grease a 9×13-inch casserole dish.
Cook pasta according to package directions. Drain and set aside.
In a large skillet, cook the chicken pieces until fully cooked. Add cooked turkey bacon and stir to combine. Remove from heat.
In a medium bowl, mix cream cheese, sour cream, milk, 1½ cups shredded cheese, diced jalapenos, and most of the green onions.
Add pasta and chicken mixture to the casserole dish. Pour sauce over everything and mix gently to coat.
Top with remaining cheese, reserved turkey bacon, and green onions.
Bake uncovered for 25–30 minutes until bubbly and lightly golden. This Chicken Casserole should rest 5 minutes before serving.