For the chicken and stuffing: Preheat the oven to 375 degrees F.
In a saucepan, heat 1 tablespoon of the oil on medium-high heat for 2 minutes. Then add the tomatoes and onions and stir. Cook this mixture until softened, 4 to 5 minutes. Season with salt and pepper and finish with minced parsley. Remove from the heat, stir and let cool. Drain off any excess liquid.
Slice a pocket in each breast from the top area next to the drumette three-quarters into the breast towards the tip. Fill each pocket with about 2 tablespoons stuffing and pat flat to ensure even cooking.
Warm an oven-safe nonstick pan over medium-high heat with the remaining 1 tablespoon olive oil for 2 minutes. Sprinkle the breasts with salt and pepper. Add the breasts to the pan, skin-side first, and allow to sear until the skin is browned, 2 to 3 minutes. Flip and cook on the second side for 2 minutes, and then place in the oven and finish for 8 to 10 minutes. Let the chicken rest until plating; keep the oil in the pan.
For the pasta: Place the heated chicken pan again over medium heat and add the onions. Cook, stirring, until softened, 3 to 4 minutes. Finally, reduce the heat to low, add the tomato sauce and stir to warm for 3 to 4 minutes. Add the pasta, stir and warm. Saucing the pasta should take 3 to 4 minutes. Add the Parmesan and stir.
Portion the pasta onto individual plates and top with a stuffed breast. Top with some Parmesan Cream and drizzle with olive oil. Garnish with parsley.
In a saucepan over medium-high heat, add the butter and cook until melted. Reduce the heat to medium, add the flour and cook, stirring, to create a roux; cook until the roux is a pale blond color. Reduce the heat to low, add the milk and cook, stirring, until thickened. Finally, add the cheese to the milk mixture one cup at a time, stirring until all the cheese has been added and well blended. Taste and season with salt and pepper, and then remove from the heat. Continue to stir to ensure consistency and to allow the mixture to cool.