Season the chicken breasts with salt, pepper, garlic powder, and oregano on both sides.
In a large oven-safe skillet, heat the olive oil over medium-high heat. Once hot, add the seasoned chicken breasts. Sear the chicken for about 4-5 minutes on each side until golden brown. Remove from skillet and set aside.
In the same skillet, reduce the heat to medium and add the heavy cream, stirring to combine with the juices from the chicken.
Add the chopped sun-dried tomatoes and cook for 2-3 minutes until everything is well blended and slightly thickened.
Stir in the fresh spinach and allow it to wilt for about a minute.
Add the grated Parmesan cheese, stir until melted and fully incorporated into the sauce.
Return the chicken breasts to the skillet, spooning the creamy sauce over them.
Transfer the skillet to the preheated oven and bake for 20-25 minutes, or until the chicken is cooked through (165°F or 75°C internal temperature).
Remove from the oven, garnish with fresh basil, and serve warm.