Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Scrub the Yukon Gold potato and dice it into uniform 1-inch cubes to ensure they cook evenly and get crispy.
In a small bowl, whisk together the extra virgin olive oil, lemon juice, minced garlic, dried oregano, sea salt, and black pepper.
Place the chicken breast and diced potatoes on the prepared sheet pan, then drizzle with half of the lemon-herb emulsion.
Toss the potatoes and chicken thoroughly to coat, then strip the rosemary leaves from the sprig and scatter them over the top.
Roast in the center of the oven for 15 minutes.
Remove the pan, add the broccoli florets, and drizzle with the remaining dressing, tossing gently to coat the vegetables.
Return the pan to the oven for another 10 to 12 minutes until the chicken reaches an internal temperature of 165°F and the potatoes are golden brown.