A friend of mine gave me the original recipe, which of course I promptly modified. This is simple and yummy! Note that the ricotta does not stay IN the shells, it blends with the sauce to make everything extra cheesy.
Preheat oven to 350. Put ricotta in a bowl, and mix herbs to taste. (recommended: garlic salt or powder, fresh ground pepper, basil/oregano, Italian herb mix.) Mix in chicken until thoroughly coated.
Spray a 13" x 9" glass casserole dish with non-stick cooking spray. Pour one can of sauce in the bottom of the pan and sprinkle with one bag of cheese. Stuff chicken-ricotta filling into the manicotti and arrange in the pan. Cover with the other can of sauce and the other bag of cheese.
Cover with foil and bake for 40 minutes. Uncover, turn the temperature up to 375 and bake for 20 more minutes. Let stand for 5 minutes after removing from oven. Serve with a spatula.