Preheat the oven to 375 degrees. Grease a 9x13 inch baking dish and set aside.
Bring a large pot of water to a boil. Add in a generous pinch of salt and cook the pasta shells according to the package directions. Drain and rinse with cold water to prevent sticking.
In a medium bowl, stir together the ricotta, 1 cup mozzarella, 1 cup parmesan, eggs, cooked chicken, and a pinch of salt and pepper.
In a large skillet over medium heat, melt the butter. Whisk in the flour and cook until the mixture turns golden brown. Whisk in the milk, then heavy cream, 1 cup parmesan, garlic and parsley. Cook, whisking constantly, until thickened.
Spread 1 cup of the sauce in the bottom of the prepared pan. Fill the shells with the chicken and cheese mixture and place them in the pan, seam side down.
Pour the remaining sauce over the shells and sprinkle with remaining mozzarella and parmesan. Bake for 25-30 minutes until the sauce is bubbling and the cheese is golden brown. Sprinkle with extra parley, if desired, and serve.
For the chicken: Use grilled, baked, or pan-fried chicken. Even rotisserie will work!
To keep the shells from sticking: drain them in a colander and immediately rinse them with cold water. If they start to stick, don’t pull them apart. Rinse them in cold water again and they should release themselves.