Heat 3 1/2 cups of the milk in a thick bottomed pan. Add the brown sugar to the milk, stir, and bring to a boil. Powder the spices and add to the remaining xbd cup of milk. Also add the custard powder to this milk. Whisk well and add to the boiling milk. Keep stirring continuously while doing this to prevent lumps from forming. The milk mixture will become a little thicker (a custard of pouring consistency). Turn off the heat and allow it to cool, while stirring occasionally to prevent a skin from forming over the top.