1️⃣ Cook the shells:
Bring a large pot of salted water to a boil. Add the jumbo shells and cook according to package directions until al dente. Drain, rinse under cold water to stop cooking, and set aside on a tray.

2️⃣ Sauté the aromatics:
In a large skillet over medium heat, warm the olive oil. Add the chopped onion and diced red bell pepper; sauté until softened, about 4–5 minutes. Stir in the garlic and cook for 1 minute more, until fragrant.

3️⃣ Build the filling:
To the skillet, add the shredded chicken, Cajun seasoning, paprika, salt, and black pepper. Stir well to coat and heat through, then transfer to a mixing bowl. Fold in the ricotta, mozzarella, and Parmesan until evenly combined.

4️⃣ Make the creamy Cajun sauce:
In a medium saucepan over medium heat, melt the butter. Whisk in the flour and cook for 1 minute to form a roux. Gradually whisk in the milk and heavy cream until smooth. Stir in the Cajun seasoning, garlic powder, and season to taste with salt and pepper. Simmer, stirring occasionally, until the sauce thickens enough to coat the back of a spoon, about 5–7 minutes.

5️⃣ Assemble the dish:
Preheat the oven to 375°F (190°C). Spread half of the sauce on the bottom of a 9×13-inch baking dish. Gently stuff each shell with about 2 tablespoons of the chicken-cheese mixture and arrange them in the dish.

6️⃣ Bake:
Pour the remaining sauce evenly over the stuffed shells. Sprinkle additional mozzarella over the top. Cover tightly with foil and bake for 20 minutes. Remove the foil and bake an additional 10 minutes, until bubbly and golden on top.

7️⃣ Rest and serve:
Let the shells rest for 5 minutes before serving. Garnish with chopped parsley or a light dusting of extra Parmesan, if desired.