Lightly crush the cinnamon stick, star anise and black peppercorns in a mortar.
Add oat milk, turmeric, ginger and crushed spices to a small pot.
Warm gently over medium-low heat and bring to a light simmer. Watch carefully, as oat milk can rise quickly.
Simmer for about 5–6 minutes, then turn off the heat and let it steep briefly.
Strain into cups.
Add honey if desired and serve warm.