Preheat the oven to 400°F (200°C).
Peel and cube the sweet potato into 1-inch pieces. Toss the cubes with half a teaspoon of olive oil, salt, and pepper, then spread them in a single layer on a baking sheet.
Roast the sweet potato cubes in the oven for 20-25 minutes until tender and slightly caramelized.
Meanwhile, prepare the chicken by patting it dry. In a small bowl, mix the chopped fresh rosemary, thyme, minced garlic, lemon zest, salt, and pepper.
Rub the herb mixture evenly over the chicken breast.
Heat a non-stick skillet over medium-high heat. Sear the chicken breast for about 2 minutes on each side until golden.
Transfer the seared chicken to a baking dish and finish cooking in the oven for an additional 10-12 minutes, or until the chicken reaches an internal temperature of 165°F (74°C).
While the chicken is baking, lightly mash the roasted sweet potato cubes with a fork or potato masher until they reach your desired consistency.
Plate the herb-crusted chicken alongside a serving of roasted sweet potato mash, and enjoy your balanced, nourishing meal.