Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Cut the chicken breast into one-inch bite-sized cubes and halve the cremini mushrooms so they are similar in size for even cooking.
In a small glass bowl, whisk together the melted ghee, olive oil, minced garlic, thyme, rosemary, sea salt, and black pepper.
Place the chicken cubes and halved mushrooms onto the prepared baking sheet and drizzle the garlic-herb mixture over the top.
Toss the ingredients thoroughly with your hands or a spatula to ensure every piece is well-coated, then spread into a single layer.
Roast in the center of the oven for 18 to 20 minutes until the chicken is cooked through and the mushrooms are tender and golden.
Remove from the oven, squeeze fresh lemon juice over the tray, and garnish with chopped parsley before serving immediately.