Preheat the oven to 375°F (190°C).

Butterfly each chicken breast by slicing it horizontally without cutting all the way through. Season both the inside and outside of the chicken with 1 ½ teaspoon of salt and ½ teaspoon of black pepper.

In a small bowl, combine the softened cream cheese, chopped sun-dried tomatoes, parsley, and a pinch of salt and pepper. Mix until smooth.

Spread the cream cheese mixture evenly inside each butterflied chicken breast. Close the chicken and secure with toothpicks to keep the filling in place.

Heat the butter and olive oil in a large skillet over medium heat. Once the butter is melted and sizzling, add the stuffed chicken breasts.

Sear the chicken for about 3-4 minutes per side, until golden brown.

Transfer the chicken to a parchment-lined baking sheet and bake for 20 minutes, or until the internal temperature reaches 165°F (74°C). Set aside to rest.

In the same skillet, melt the butter over medium heat. Add the diced onion and 1 teaspoon of salt, sautéing for 5 minutes until the onion turns soft and translucent.

Pour in the heavy cream and let it cook, stirring frequently, until it thickens, about 5 minutes.

In a small bowl, whisk the flour with 3 tablespoon of water until smooth. Stir the flour mixture into the sauce and cook for another 5 minutes until the sauce thickens further.

Stir in the grated Parmesan cheese, ground nutmeg, and fresh spinach. Simmer until the spinach wilts, about 3-5 minutes.

Add the cooked rigatoni to the skillet and toss to coat the pasta evenly in the creamy spinach sauce.

Plate the creamy spinach rigatoni and top with the stuffed chicken breasts. Serve immediately and enjoy!