Pre-heat oven to 400F.
Cook pasta shells according to the directions on the package, drain and set aside.
While the pasta is cooking, dump the shredded chicken into a large mixing bowl.
Add the ricotta cheese, shredded mozzarella cheese, shredded parmesan cheese, salt, pepper, onion powder, garlic powder, and Italian seasoning to the bowl. Stir all of the ingredients together until fully combined and then set aside.
Pour the heavy cream into a large sauté pan over medium heat. Add the salt, pepper and garlic powder to the cream and mix.
Increase the heat to bring the cream to a boil. Once the cream is boiling, quickly reduce the heat back to medium and leave the cream to simmer and thicken, stirring occasionally.
After 5 minutes remove the pan from the heat and add the shredded parmesan cheese to the sauce. Whisk until cheese is melted into the sauce. This is a good time to add additional seasoning if you so desire.
Add approximately 1/3 of the sauce into the bottom of a greased 9 x 13 inch baking dish.
Spoon the chicken and cheese mixture into the cooked pasta shells and place them in a single layer on top of the sauce in the baking dish.
Pour the remaining sauce over the stuffed shells and sprinkle the shredded mozzarella cheese on top of the stuffed shells.
Place the baking dish in the oven and bake the pasta until the sauce is bubbling and the cheese on top is starting to brown about 30-35 minutes.
Remove the dish from the oven and sprinkle the parsley flakes on top. Allow the pasta to sit for about 5 minutes before scooping and serving so sauce can set.