Preheat your oven to 425°F (220°C), or 200°C for fan ovens.
Place chicken breasts on a cutting board and cover with plastic wrap or parchment paper. Pound the thickest parts until each breast is about 1.5 cm thick for even cooking.
In a small bowl, mix brown sugar, paprika, dried oregano or thyme, garlic powder, salt, and black pepper until fully combined.
Line a baking tray with foil and place parchment paper on top for easy cleanup.
Place chicken breasts on the tray smooth side down. Drizzle half of the olive oil over the chicken and rub evenly. Sprinkle half of the seasoning mix over the chicken.
Flip the chicken breasts over. Drizzle the remaining olive oil and rub evenly. Sprinkle the rest of the seasoning mix over all pieces.
Bake for about 18 minutes, or until the chicken reaches an internal temperature of 165°F (75°C). For extra juicy chicken, remove at 160°F (71°C) and let carryover cooking finish the job.
Transfer chicken to serving plates and let rest for 3 to 5 minutes before slicing.
Garnish with freshly chopped parsley if desired and serve warm with your favorite side dishes.