Bring a large pot of salted water to a boil. Cook the jumbo pasta shells according to package instructions until al dente. Drain and rinse with cold water to stop cooking. Set aside.
In a large mixing bowl, combine the shredded chicken, cream cheese, buffalo sauce, mozzarella cheese, Parmesan cheese, garlic powder, onion powder, salt, and pepper. Mix until combined and creamy.
Using a spoon, fill each cooked pasta shell generously with the buffalo chicken mixture. Place the stuffed shells in a greased 9x13-inch baking dish.
In a small bowl, mix the heavy cream with a couple of tablespoons of buffalo sauce (to taste) and pour it over the stuffed shells, ensuring they are well-coated.
Sprinkle additional mozzarella cheese over the top of the shells.
Cover the baking dish with foil and bake for 25 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and slightly golden.
Remove from oven and sprinkle with chopped green onions before serving.
Notes
Adjust buffalo sauce according to heat preference.