Season the chicken breasts with salt and pepper. In a large skillet, heat the olive oil over medium heat. Add the chicken and cook for about 5-7 minutes on each side, or until golden brown and cooked through. Remove the chicken from the skillet and set aside.

In the same skillet, add the diced onion and cook for 3-4 minutes until softened. Add the minced garlic and sliced mushrooms, cooking for an additional 3-4 minutes until the mushrooms are tender.

Stir in the orzo pasta, chicken broth, Marsala wine, and dried thyme. Bring the mixture to a boil, then reduce the heat to low. Cover and simmer for about 10-12 minutes, or until the orzo is tender and has absorbed most of the liquid.

While the orzo cooks, slice the cooked chicken into strips. Once the orzo is ready, stir in the heavy cream and Parmesan cheese until well combined. Add the sliced chicken back to the skillet and mix gently to combine.

Cook for an additional 2-3 minutes until heated through. Garnish with fresh parsley before serving.