I find it easier to cut my chicken into small pieces if it is only partially-thawed (if frozen), or I put it in the freezer for about an hour to firm it up, then cut.
In a large skillet, heat 1 tblsp of oil over high heat until hot but not smoking; brown chicken and transfer to a bowl.
Heat remaining tblsp of oil until hot but not smoking and saute onions and mushrooms, stirring, for 2-3 minutes, or until golden.
Add Sherry and deglaze skillet, stirring and scraping up brown bits.
Stir in broth, cream cheese, garlic, mustard and thyme. Season with salt and pepper to suit your taste. Boil gently for 3 minutes, whisking to incorporate cream cheese and mustard into sauce. Add chicken and any juices that have collected in bowl and cook 8-10 minutes longer. Taste and adjust seasoning.
Arrange noodles or rice or mashed potatoes on a platter, spoon chicken and sauce over and sprinkle with parsley.