Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Cut the chicken breast into 1-inch bite-sized pieces and halve or quarter the cremini mushrooms so they are similar in size to the chicken.
In a small glass bowl, melt the ghee and whisk in the minced garlic, chopped thyme, chopped rosemary, sea salt, and black pepper.
Place the chicken and mushrooms on the prepared baking sheet and pour the garlic-herb ghee mixture over them, tossing thoroughly to ensure every piece is well coated.
Spread the mixture into a single layer, ensuring no pieces are overlapping, and roast for 18 to 20 minutes until the chicken is cooked through and the mushrooms are golden brown.
Remove from the oven, drizzle with fresh lemon juice for brightness, and garnish with freshly chopped parsley before serving.