Boil a large pot of salted water, and cook the jumbo shells according to package instructions until al dente. Drain and set aside to cool slightly.
In a skillet, heat the olive oil over medium heat. Add the diced onion and minced garlic, and sauté until the onion is translucent. Add chopped spinach and cook until wilted.
In a mixing bowl, combine the shredded chicken, ½ cup of Cajun seasoning, sautéed vegetables, ricotta cheese, and ½ cup of mozzarella cheese. Season with salt and pepper to taste.
Stuff each cooked shell with a generous amount of the chicken mixture, placing the filled shells in a greased baking dish.
Pour the Alfredo sauce evenly over the stuffed shells, ensuring all shells are covered. Sprinkle the remaining mozzarella cheese and Parmesan cheese over the top.
Place the baking dish in the oven and bake for 25-30 minutes, or until the cheese is bubbly and golden brown.
Remove from the oven and let cool slightly. Garnish with fresh parsley before serving.
Notes
Feel free to adjust the amount of Cajun seasoning to your taste.