Preheat oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish.
Pat the chicken breasts completely dry with paper towels. Rub each piece with olive oil, then season generously with salt, black pepper, garlic powder, and paprika.
Optional: Heat a skillet over medium-high heat and sear chicken for 2 to 3 minutes per side until golden brown. Transfer to prepared baking dish.
In a small bowl, whisk together heavy cream, Parmesan cheese, Dijon mustard, lemon juice, and thyme until smooth and well combined.
Pour the Parmesan sauce evenly over the chicken breasts in the baking dish, making sure each piece is well coated.
Cover the dish with aluminum foil and bake for 20 to 25 minutes, or until chicken reaches an internal temperature of 165°F (74°C).
Remove foil during the last 5 minutes of baking for a lightly golden top.
Let the chicken rest for 5 minutes before slicing. Garnish with fresh parsley and serve with sauce spooned over top.