In a large saucepan, combine the apple cider, sliced orange, cinnamon sticks, whole cloves, whole allspice berries, sliced ginger (if using), and star anise (if using).
Bring the mixture to a gentle simmer over medium heat. Do NOT let it boil, as boiling can diminish the fresh apple flavor.
Once simmering, reduce the heat to low, cover the saucepan, and let the cider steep for at least 20-30 minutes. The longer it steeps, the more intense the spice flavors will become.
Taste the cider. If you prefer it sweeter, stir in your chosen sweetener (maple syrup, brown sugar, or honey) until dissolved.
Carefully strain the cider through a fine-mesh sieve or cheesecloth into a clean pot or directly into mugs to remove the spices and orange slices.
Serve the mulling spice cider hot, ladling it into mugs.