Step 1: Prepare the Chicken

1. Place the chicken breasts between two sheets of plastic wrap and pound to an even thickness of about 1/2 inch.
2. In a shallow dish, combine flour, garlic powder, onion powder, salt, and black pepper. Dredge each chicken breast in the mixture, shaking off excess flour.

Step 2: Cook the Chicken

1. Heat olive oil and butter in a large skillet over medium-high heat.
2. Add the chicken breasts and sear for 4–5 minutes per side until golden brown and cooked through. Transfer the chicken to a plate and tent with foil to keep warm.

Step 3: Sauté the Mushrooms

1. In the same skillet, add the mushrooms and cook over medium heat for 5–7 minutes until they release their moisture and begin to brown.
2. Stir in the garlic and cook for another 30 seconds until fragrant.

Step 4: Deglaze with Marsala Wine

1. Pour the Marsala wine into the skillet, scraping up any browned bits from the bottom of the pan.
2. Allow the wine to simmer for 2–3 minutes to reduce slightly.

Step 5: Create the Creamy Sauce

1. Stir in the chicken broth and thyme, bringing the mixture to a gentle simmer.
2. Add the heavy cream and cook for 3–4 minutes until the sauce thickens. If a thicker sauce is desired, stir in the cornstarch slurry and cook for an additional minute.

Step 6: Combine and Serve

1. Return the chicken breasts to the skillet, spooning the sauce over the top. Simmer for 2–3 minutes to heat through.
2. Garnish with fresh parsley and serve immediately with your choice of sides.