Preheat your grill to medium-high heat. (You can also use a grill pan.) Season both sides of the chicken breasts with garlic powder, onion powder, Italian seasoning, salt, and pepper.
Grill the chicken for 6-7 minutes per side, or until the internal temperature reaches 165°F. Remove from the grill and let it rest.
While the chicken rests, melt the light butter in a skillet over medium heat. Add the garlic and cook for about 30 seconds until fragrant.
Whisk in the fat-free half-and-half and softened cream cheese until smooth.
Stir in the Parmesan cheese and Dijon mustard. Simmer for 3-5 minutes, stirring frequently, until the sauce thickens slightly.
Spoon the creamy sauce over the grilled chicken and garnish with fresh parsley.