2teaspoonsred rooibus teaor black tea if you don't mind the caffeine
Place the cardamom pods in a mortar and pestle and give them a gentle grind to break them open and release the seeds, then add to a pot with the 3 cups of water. Grind the star anise and fennel in the same way, then add to the pot.
Slice the vanilla bean lengthwise, then add to the pot along with the grated nutmeg, cinnamon, ginger, and peppercorns (basically everything but the rooibus/black tea and oat milk!).
Bring the water to a boil then reduce to a simmer, cover slightly and leave it to reduce to about 2 cups – this may take between 15 and 20 minutes.
Add the oat milk and black tea, bring the water to a boil again then reduce to a simmer for five minutes.