In a small bowl, prepare the filling by combining sour cream, sun-dried tomatoes, and parmesan cheese. Set it aside.
Cut the chicken breast lengthwise to create a pocket, ensuring the chicken breast is not cut through.
Stuff the chicken pocket with about 2 tablespoons of prepared filling, top it with a layer of mozzarella cheese and seal the chicken with a toothpick.
Season the chicken breasts with Italian seasonings, salt, and pepper.
Heat a skillet on a medium flame with oil. Once the oil is heated, sear the chicken breast on both sides until slightly golden for 5-6 minutes. Once done, remove the chicken from a plate and set it aside.
To the same skillet, add butter. Once the butter is melted, add the garlic and mushroom and cook for 2-3 minutes.
Stir in the Marsala wine and allow it to simmer for a couple of minutes.
Pour the whipping cream and red pepper flakes and let it simmer until the sauce begins to slightly thicken. Season the sauce with salt and pepper.
Transfer the chicken back to the skillet with the juices from the chicken and cook for 3-5 minutes on low heat.
Once done, garnish the chicken Marsala stuffed chicken with chopped parsley.
Serve the creamy chicken with the greens on the side or over pasta/mashed potatoes/rice/noodles.