Preheat oven to 350F.

Cook pasta shells in boiling water according to the package directions. Drain and rinse with cold water to prevent them from cooking further. Set aside.

Coat a 9 x 13-inch pan with cooking spray. Spread 1/2 cup of sauce evenly over bottom of pan and set aside.

For filling, in a large bowl, stir together egg whites, ricotta cheese, chicken, spinach, garlic powder and seasoning. Stir in 1/4 cup each of mozzarella cheese and Parmesan cheese.

To assemble, spoon cheese mixture into the pasta shells and place filled shells in a single layer in baking dish. Spread remaining sauce on top. Sprinkle with remaining cheeses and bake about 30 minutes. Yields 3 shells per serving.