In a large skillet over medium heat add 1 tablespoon olive oil to the pan. Add the chicken and lightly salt and pepper. Cook until lightly brown and cooked throughout. Remove chicken and set aside on plate.
Add 1 Tablespoon olive oil and sauté the mushrooms for 1-2 minutes. Add marsala wine and bring to a boil over medium high heat for 1-2 minutes. This allows the alcohol to burn out. Add the chicken broth, heavy whipping cream, ground mustard, and garlic powder.
Bring to a boil and reduce heat and simmer for about 10 minutes or until it starts to thicken. Place chicken back in the sauce and continue to simmer for about 1-2 minutes.
** The alcohol will burn out during the cooking process but if you are worried about cooking with wine you can use this as a substitute:1/4 cup white grape juice, 1 T Vanilla Extract, 2 T Sherry Vinegar.