Saute mushroom in a wok over high heat for 1 minute with 1 Tbsp of oil. Reduce the heat to medium and stir fry until the mushrooms are tender, about 3-5 minuts. Set aside
In the same wok, add 1 Tbsp of oil and saute chicken until they are cooked through. Set aside
In a large sauce pan, combine coconut milk, stock, galangal, lemon grass, chili, lime leaves and peppercorns. Bring to boil and then simmer uncovered for 15 minutes
Add in fish sauce, lime juice, palm sugar, mushrooms and chicken. Simmer for 3 minutes. Adjust seasoning as needed