Preheat the oven to 375°F (190°C).
Cook the jumbo pasta shells according to package instructions until al dente.
In a large bowl, combine shredded chicken, mascarpone, half the cheddar, bell peppers, green onions, Cajun seasoning, salt, and black pepper.
Fill each cooked pasta shell with the chicken mixture, and place them in a greased baking dish.
In a separate saucepan, heat heavy cream over medium heat and simmer for 5 minutes until slightly thickened.
Pour the cream over the stuffed shells, and sprinkle with the remaining cheddar cheese.
Cover the dish with aluminum foil and bake for 20 minutes.
Remove the foil and bake for an additional 15 minutes until the cheese is bubbly and golden.
Garnish with chopped parsley before serving.
