Pour the apple juice into a saucepan and add the sugar, lemon slices, orange peel, cinnamon sticks, cloves, cardamom pods, star anise, vanilla seeds and the empty pod.
Set the hob to medium and let it simmer for 20-30 minutes. It should not boil, just simmer until the sugar has dissolved and the spices have released a good aroma.
Scald a preserving jar or similar with boiling water, pour in both the port and the rum, then pour in the contents of the pan, spices and all.Put the lid on and refrigerate for 2 days.
After 2 days, remove the lemon slices, and the extract is ready to use. It can happily steep for longer, though, so feel free to leave it in the fridge with the spices still in – they give plenty of lovely flavour.
Strain out the spices when you are ready to use the extract. I pour the amount I need through a fine-mesh sieve and leave the spices in the rest of the extract in the fridge.I mix 150 ml extract with 1 bottle of white wine - but experiment. You may prefer it milder or stronger.