Preheat the oven to 350°F (175°C). In a skillet, heat the olive oil over medium heat. Add the mushrooms and garlic, cooking until the mushrooms are tender.

In a large bowl, combine the cooked chicken, sautéed mushrooms and garlic, heavy cream, and half of the cheese. Season with salt and pepper to taste.

Transfer the mixture to a greased casserole dish and top with the remaining cheese.

Bake in the preheated oven for 25-30 minutes, until bubbly and golden. Garnish with fresh parsley if desired and serve hot.