Pat the chicken breasts dry with paper towels. Pound them to an even thickness if necessary.
Season both sides with garlic powder, onion powder, paprika, thyme, salt, and black pepper.
Heat the olive oil in a large skillet over medium-high heat.
Cook the chicken breasts for 5 to 6 minutes per side until golden brown. Remove them from the skillet and set aside.
Reduce the heat to medium. Add the butter and minced garlic, then cook for 30 seconds until fragrant.
Pour in the chicken broth and stir to loosen any browned bits from the bottom of the skillet.
Whisk in the Dijon mustard, heavy cream, lemon juice, and Parmesan cheese if using. Simmer for 2 to 3 minutes until the sauce begins to thicken.
Return the chicken to the skillet and spoon the sauce over the top.
Cook for another 3 to 5 minutes, or until the chicken reaches an internal temperature of 165°F (74°C).
Let the chicken rest for 5 minutes before serving.
Garnish with fresh parsley and spoon the creamy Dijon sauce over each chicken breast.