Preheat your oven to 400°F (200°C) and line a rimmed baking sheet with parchment paper for easy cleanup.
Pat the chicken breast dry with paper towels and cut into uniform 1-inch cubes to ensure even cooking.
Clean the cremini mushrooms with a damp cloth and slice them into halves or quarters depending on their size.
In a large mixing bowl, whisk together the melted ghee, minced garlic, sea salt, and black pepper.
Add the chicken cubes and mushrooms to the bowl, tossing thoroughly until every piece is coated in the garlic-ghee mixture.
Spread the mixture onto the prepared baking sheet in a single layer, ensuring they are not overcrowded so they roast rather than steam.
Roast for 18 to 22 minutes, or until the chicken reaches an internal temperature of 165°F and the mushrooms are tender.
Remove from the oven, drizzle with fresh lemon juice to brighten the flavors, and garnish with chopped parsley.