Preheat your oven to 425°F and line a baking sheet with parchment paper.
Wash the Yukon gold potato and dice it into uniform 1/2-inch cubes for even roasting.
Mince the garlic cloves and finely chop the fresh rosemary leaves.
In a medium mixing bowl, toss the potato cubes with 0.5 tbsp of olive oil, half of the minced garlic, the rosemary, and a pinch of the salt and pepper.
Spread the potatoes in a single layer on the prepared baking sheet and roast for 20-25 minutes until the edges are golden and crispy.
While potatoes roast, season the chicken breast on both sides with the remaining salt and pepper.
Heat the remaining 0.5 tbsp of olive oil in a cast-iron skillet or heavy pan over medium-high heat.
Place the chicken in the skillet and sear for 5-7 minutes per side, or until the internal temperature reaches 165°F and the exterior is nicely browned.
During the last 2 minutes of the chicken cooking, add the remaining garlic and the fresh baby spinach to the skillet, stirring until the spinach is just wilted.
Plate the crispy roasted potatoes alongside the pan-seared chicken and sautéed greens, serving immediately while hot.