Cook the fettuccine pasta according to package instructions until al dente. Drain and set aside, reserving 1/2 cup of the pasta cooking water.
Season the sliced chicken with salt and pepper. In a large skillet, heat the olive oil over medium-high heat. Add the chicken and cook until browned and cooked through, about 5-7 minutes. Remove the chicken from the skillet and set aside.
In the same skillet, add the sliced mushrooms and cook until they are browned and tender, about 5 minutes. Add the minced garlic and cook for an additional minute until fragrant.
Pour in the Marsala wine, scraping up any browned bits from the bottom of the skillet. Let it simmer for about 2-3 minutes until slightly reduced.
Add the chicken broth and bring to a simmer. Stir in the heavy cream and let it cook for another 2-3 minutes until the sauce thickens slightly.
Return the cooked chicken to the skillet and toss to coat in the sauce. If the sauce is too thick, add some reserved pasta cooking water to reach desired consistency.
Add the cooked fettuccine to the skillet and toss everything together until well combined. Stir in the grated Parmesan cheese and mix until melted and creamy.
Serve immediately, garnished with fresh parsley.
Notes
For a lighter version, substitute the heavy cream with half-and-half or a non-dairy alternative.
Add spinach or kale to the dish for extra greens and nutrients; toss it in during the last few minutes of cooking until wilted.