Pour both bottles of wine into a large saucepan or stockpot. Add the orange juice and place over medium-low heat.
Add all the sliced citrus fruits to the wine along with the cinnamon sticks, cloves, star anise, and split vanilla pod.
Stir in the honey or maple syrup and add a generous grating of fresh nutmeg (about 1/4 teaspoon).
Let the mixture heat gently for 15-20 minutes—don't let it boil or you'll cook off all the alcohol! You want it steaming and fragrant.
Stir in the brandy if using, then taste and adjust sweetness if needed.
Keep warm on the lowest heat setting and ladle into heatproof glasses or mugs, making sure each serving gets a few spices and citrus slices for presentation.