Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Pat the chicken breast dry with paper towels and cut into 1-inch bite-sized pieces.
Clean the cremini mushrooms with a damp cloth to remove any debris and slice them in half.
In a small bowl, melt the ghee and whisk in the minced garlic, fresh thyme leaves, sea salt, and black pepper.
Place the chicken pieces and halved mushrooms on the prepared baking sheet.
Drizzle the garlic-herb ghee mixture over the chicken and mushrooms, tossing thoroughly to ensure every piece is well coated.
Spread the mixture into a single layer, ensuring no pieces are overlapping to allow for even browning.
Roast in the center of the oven for 18-20 minutes, or until the chicken is cooked through and the mushrooms are golden and tender.
Remove from the oven, drizzle with fresh lemon juice, and garnish with chopped fresh parsley before serving warm.