Cook the pasta shells according to package instructions until al dente.
Preheat your oven to 350°F (175°C).
In a skillet, heat olive oil over medium heat and add minced garlic.
Add the chicken and cook until browned and fully cooked, about 7-10 minutes.
Shred the cooked chicken using two forks.
In a bowl, combine ricotta cheese, mozzarella cheese, Parmesan cheese, Cajun seasoning, heavy cream, and shredded chicken.
Carefully stuff each pasta shell with the chicken mixture.
Spread a layer of marinara sauce on the bottom of a baking dish.
Place the stuffed shells in the dish and top with remaining marinara sauce and cheese.
Cover the baking dish with aluminum foil.
Bake for 25-30 minutes, then uncover and bake for an additional 10 minutes.
Let cool for a few minutes before serving, garnishing with green onions.