Preheat oven to 425°F.: The moment you switch on the oven you will smell the faint warmth of the element coming alive, which primes the pan for even cooking. Preheating ensures the chicken starts to sear and the sauce begins to bubble properly in the hot environment. If the oven is not fully heated, the chicken may cook unevenly and the sauce will take longer to thicken. A common mistake is to start baking before the oven reaches temperature, which lengthens cooking time and can dry the meat.
Place the chicken breast in a plastic bag or cover with plastic wrap. Use a rolling pin to pound to even thickness. Place the chicken once ready in an oil sprayed 9×13 inch baking pan. Season the chicken with the salt, pepper, garlic, Italian seasoning, crushed red pepper and paprika. Place the mushrooms and chopped sun-dried tomatoes in the baking pan surrounding the chicken.: As you pound the chicken you will feel the meat relax and become uniform, which helps it cook at the same rate. Lay the breasts flat and season them so the spices adhere; you should see a light coating of herbs and specks of paprika. Arrange the sliced mushrooms and chopped sun dried tomatoes around the meat so they can roast slightly and contribute roasted aromas. Be mindful not to overpack the pan, or the vegetables will steam instead of browning. One slip is using uneven thicknesses, which results in some pieces over cooked while others are underdone.
In a small bowl, whisk together the broth and corn starch until corn starch is fully dissolved. Add the cream, cream cheese, garlic, salt and pepper (as desired) and whisk well until smooth. Stir in the parmesan and pour the mixture over top of the chicken, mushrooms and tomatoes.: When you whisk the chicken broth and cornstarch, look for a uniform, slightly viscous mixture with no lumps, that is your signal that it will thicken properly. Adding softened cream cheese into warm liquid produces a silky texture, and stirring in freshly grated parmesan melts it into a glossy finish. Pour slowly so the sauce envelopes the chicken and settles among the vegetables. If the cornstarch was not fully dissolved, you may see specks or uneven thickening; take time to fully emulsify the mixture.
Bake in preheated oven for about 17-20 minutes or until the chicken reaches almost 165°F (I usually remove the chicken at 162° or 163°). Add the chopped spinach to the cream mixture and allow to wilt and the chicken to rest to come to temperature.: In the oven you will hear a gentle sizzle as the sauce bubbles and the edges of the mushrooms darken. The surface of the sauce may shimmer and the aromas of garlic and herbs will become more pronounced. Pulling the chicken slightly shy of 165°F and letting carryover heat finish it helps keep the meat juicy. Fold the chopped spinach into the hot sauce so it wilts quickly into vibrant green ribbons. Avoid over baking which yields dry texture; rely on a thermometer for accuracy.
Serve as desired over top pasta or with your favorite side dishes. Store leftovers in an air tight container for about 4 days in the refrigerator.: The finished dish will present with a creamy, glossy sauce pooling around golden edged chicken and soft, reduced mushrooms . Serve hot so the sauce feels silky on the tongue. For storage, cool the pan briefly, then transfer to airtight containers; the sauce thickens as it chills so reheat gently to loosen it. A frequent error is reheating too quickly on high heat, which can separate the sauce or dry the meat, so use moderate heat when warming leftovers.
