Preheat your oven to 375°F (190°C).

In a small bowl, combine Cajun seasoning, garlic powder, smoked paprika, salt, and black pepper. Rub the spice mixture all over the chicken breasts.

Heat olive oil in a large skillet over medium heat. Add the chicken breasts and cook for 4-5 minutes per side until golden brown. The chicken doesn’t need to be fully cooked at this point, as it will continue cooking in the oven. Remove from the skillet and set aside.

In a medium bowl, mix spinach, roasted red peppers, 1/2 cup mozzarella cheese, ricotta cheese, Parmesan cheese, and the beaten egg until well combined.

Slice a pocket into each chicken breast horizontally, being careful not to cut all the way through. Stuff each chicken breast with the spinach and cheese mixture, securing the opening with toothpicks if needed.

In the same skillet, melt the butter over medium heat. Add the flour and cook, whisking constantly for 1-2 minutes to create a roux.

Gradually add chicken broth and milk, whisking continuously until the sauce thickens and becomes smooth, about 5 minutes. Stir in the remaining mozzarella cheese and heavy cream. Season with salt and pepper to taste.

Place the stuffed chicken breasts back into the skillet and spoon some of the sauce over them. Transfer the skillet to the preheated oven and bake for 20-25 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and the filling is hot.

Once cooked, remove the toothpicks from the chicken breasts. Serve the chicken with the creamy sauce from the skillet spooned over the top.