Preheat oven to 350 degrees. Spray a 9X13 pan with cooking spray.

In a large non-stick skillet, heat butter over medium heat. Add the chicken and brown for 3-4 minutes. Add the mushrooms, green onions and garlic and cook until chicken is done and mushrooms are golden brown.

Sprinkle flour over chicken mixture and stir to combine. Cook for 1-2 minutes. Add the chicken broth and cook and stir until thickened. Mix in sour cream and stir until well combined. Stir in the uncooked tortellini.

Pour the chicken and tortellini mixture into the prepared pan. Sprinkle with cheese. Bake, covered with foil, for 25 minutes. Uncover and bake for an additional 10 minutes or until bubbly and golden brown around the edges.