Preheat your oven to 400°F (200°C).
Slice the cremini mushrooms into thick pieces and finely mince the garlic cloves.
Pat the chicken breast dry with a paper towel and season both sides evenly with sea salt and black pepper.
Heat the extra virgin olive oil in a large oven-safe skillet over medium-high heat.
Sear the chicken for 3 to 4 minutes per side until a golden-brown crust forms, then temporarily remove the chicken from the pan.
In the same skillet, add the ghee and the sliced mushrooms, sautéing for about 3 minutes until they release their moisture and begin to brown.
Stir in the minced garlic and fresh thyme, cooking for 1 minute until highly fragrant.
Place the chicken breast back into the skillet, nestling it among the mushrooms, and transfer the pan to the oven.
Roast for 10 to 12 minutes or until the chicken reaches an internal temperature of 165°F.
Serve the roasted mushrooms and garlic butter sauce over the chicken on a bed of fresh baby spinach.