Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Pat the chicken breast dry with a paper towel and cut into uniform 1-inch cubes.
Clean the mushrooms with a damp cloth and slice them into halves or quarters if they are large.
Mince the garlic cloves and finely chop the fresh thyme and rosemary leaves.
In a large mixing bowl, combine the chicken, mushrooms, melted ghee, olive oil, minced garlic, herbs, salt, and pepper.
Toss everything thoroughly until the chicken and mushrooms are evenly coated in the herb fat.
Spread the mixture onto the prepared baking sheet in a single layer, ensuring they are not overcrowded.
Roast for 18 to 20 minutes, tossing halfway through, until the chicken reaches an internal temperature of 165°F and the mushrooms are tender.
Remove from the oven and drizzle with fresh lemon juice to brighten the flavors before serving.