In a small saucepan, combine the water, cardamom, ginger, cinnamon stick and star anise. Bring the mixture to a boil then lower the heat and simmer for a few minutes until the mixture is fragrant. Add the milk and tea leaves, and simmer for another minute then turn off the heat and let steep for 2 minutes. Pour into a cup through a fine mesh sieve. Discard the leaves and spices. Add sweetener, to taste.