Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Trim and halve the Brussels sprouts, then toss them with half of the olive oil, a pinch of salt, and pepper.
Place the seasoned Brussels sprouts on the baking sheet and roast in the preheated oven for about 20-25 minutes, stirring halfway through for even crisping.
Meanwhile, pat the chicken breast dry. In a small bowl, whisk together the remaining olive oil, minced garlic, lemon juice, mixed fresh herbs, salt, and pepper.
Rub the herb mixture evenly over the chicken breast.
Heat a skillet over medium-high heat and sear the chicken on both sides for about 2 minutes per side until lightly browned.
Transfer the seared chicken to an oven-safe dish and place in the oven alongside the Brussels sprouts for an additional 10-12 minutes, or until the chicken reaches an internal temperature of 165°F (74°C).
Remove both the chicken and Brussels sprouts from the oven. Let the chicken rest for a few minutes before slicing and serving with the crispy Brussels sprouts.