Heat oil in a wok and fry the crushed and knotted sereh on medium heat. After 3 minutes add the unrubbed bumbu and stir fry to a high heat, about 3 to 4 minutes. Then add the other half of the bumbu and lower the heat. Let the bumbu cook for 5 minutes and then add the coconut cream. Bring to temperature and allow to thicken to the desired thickness. Season with salt and pepper.