Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Halve the cremini mushrooms and toss them on the baking sheet with the broccoli florets, olive oil, half of the sea salt, and half of the black pepper.
Season the chicken breast with the remaining sea salt and black pepper, then sear in a hot oven-safe skillet for 3 minutes per side until golden.
Place the baking sheet with the vegetables in the oven and roast for 15 to 20 minutes until the mushrooms are tender and the broccoli is crisp-tender.
In the last 5 minutes of roasting, place the skillet with the chicken into the oven to finish cooking until the internal temperature reaches 165°F.
While the chicken rests, melt the ghee in a small saucepan over medium heat, add the minced garlic and fresh thyme, and sauté for 1 to 2 minutes until fragrant.
Slice the chicken breast and plate it alongside the roasted vegetables, drizzling the warm garlic thyme butter over the mushrooms and chicken before serving.