Place the tapioca in a heavy-bottomed saucepan along with the coconut milk, cardamom pods, and cinnamon stick.
Bring to a boil, watching the pot since the milk can easily boil over and create a mess to clean up later!
Lower the heat to a simmer, cover, and cook while stirring frequently. The cook time will take 45–60 minutes.
Cook until the mixture is slightly thick but is easy to stir. The pudding will continue to thicken even after the heat is turned off.
Remove the cinnamon stick and cardamom pods and gently stir in the ginger powder and stevia.
Garnish with pistachio nuts and serve warm.