Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Slice the chicken breast into even 1-inch bite-sized pieces to ensure they cook quickly and stay juicy.
Clean the cremini mushrooms with a damp cloth and quarter them so they have plenty of surface area to get golden brown.
In a small bowl, whisk together the melted ghee, minced garlic, sea salt, black pepper, and fresh thyme until well combined.
Place the chicken and mushrooms in a large mixing bowl, pour the garlic-ghee mixture over them, and toss thoroughly to coat every piece.
Spread the mixture in a single layer on the prepared baking sheet, making sure not to crowd the pan so the mushrooms roast rather than steam.
Roast in the oven for 18 to 20 minutes, or until the chicken is cooked through and the mushrooms are tender and caramelized.
Remove from the oven and garnish with freshly chopped parsley for a bright, herbaceous finish before serving.