Chicken Preparation: Commence by ensuring the chicken breasts are appropriately sliced. If required, halve them horizontally to achieve the desired thickness. Drying the chicken with paper towels is imperative to remove any excess moisture.

In a deep bowl, meticulously combine the flour, salt, pepper, garlic powder, and Italian seasoning. Submerge each chicken breast in the mixture, ensuring an even coat on both surfaces. Once completed, set aside.

Chicken Cooking Procedure: In a large skillet, heat the olive oil over medium-high heat. When the oil reaches its optimal temperature, introduce the chicken breasts. Cook each side until a golden-brown hue is achieved, approximately 4-5 minutes per side. Following this, place the chicken in a separate dish for subsequent use.

Sauce Preparation: In the residual oil in the skillet, introduce the butter, finely diced yellow onion, and minced garlic. Sauté until the ingredients attain a translucent quality. Following this, incorporate the scallions and tomatoes. Sprinkle the flour and blend thoroughly to ensure even distribution.

Gradually introduce the heavy cream, wine, and the selected seasonings into the skillet. Once a consistent blend is achieved, add the freshly shredded Parmesan cheese, stirring continuously until a harmonious consistency is formed.

Pasta Cooking Procedure: In a large pot, boil the spaghetti as per the manufacturer’s guidance, ensuring it retains a firm texture. Once cooked, drain the water and avoid rinsing the pasta to retain its starch.

Final Assembly: Transfer the cooked pasta to the skillet containing the sauce, gently merging the two over low heat. Subsequently, place the chicken over the pasta and let the ensemble simmer for an additional duration of 5 minutes. Prior to serving, garnish with additional Parmesan cheese if so desired.