Season chicken with salt and pepper. Heat oil in large nonstick skillet. Add onion and garlic; sauté until softened, about 3 minutes. Add mushrooms; sauté until lightly browned, about 3 minutes. Add paprika and chicken; sauté until chicken turns white, 3 minutes.
Stir 3 tablespoons sherry, chicken broth and sour cream in small bowl until smooth. Add to skillet. Simmer, covered, about 8 minutes or until chicken is cooked through.
Stir remaining sherry, flour and mustard in cup until smooth. Add to skillet; bring to boiling, stirring. Serve over noodles or rice if desired. Garnish with parsley.