In a pot of salted, boiling water, cook the noodles, according to package directions until al dente. Rinse and drain well. Set aside.
Preheat the oven to 350 degrees. Spray a 9x13-inch baking pan with nonstick cooking spray.
Combine the chicken, cream cheese, 1 cup mozzarella cheese, scallions, and herbed seasoning mix. Mix until the ingredients are well incorporated.
Divide the chicken mixture among the cooked shells. Place the shells in the prepared pan. Pour the sauce over all and sprinkle with the remaining cup of cheese.
At this point, you can wrap and label the pan, if freezing. Chill completely before freezing.
If baking fresh, bake for 30 minutes until hot and bubbly. If baking from frozen, thaw the shells in the refrigerator before baking.