Preheat your oven to 400°F and line a large 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 to remove any grit and slice them in half or quarters if they are large.
In a large mixing bowl, whisk together the melted ghee, extra virgin olive oil, minced garlic, chopped thyme, rosemary, sea salt, and black pepper.
Add the chicken cubes and mushrooms to the bowl and toss thoroughly until every piece is well-coated in the herb fat mixture.
Spread the chicken and mushrooms in a single layer on the prepared baking sheet, making sure not to crowd the pan so they roast rather than steam.
Place the pan in the center of the oven and roast for 18-20 minutes, tossing halfway through, until the chicken is cooked through and the mushrooms are deeply browned.
Remove from the oven, drizzle with fresh lemon juice, and garnish with chopped parsley before serving immediately while hot.