Prepare the orange: Wash the orange thoroughly. Carefully push the whole cloves into the skin of the orange, spacing them evenly. This helps release their flavor and makes them easy to remove later.

Combine ingredients in a pot: In a medium-sized saucepan or Dutch oven (at least 2-liter or 2-quart capacity), combine the 750ml (1 bottle) of red wine, the studded orange, 2 cinnamon sticks, 2 star anise, 50g (1/4 cup) of brown sugar, and 120ml (1/2 cup) of water.

Heat gently: Place the saucepan over medium-low heat. Stir gently to help the brown sugar dissolve. Do NOT bring the mixture to a boil. Simmering or boiling will evaporate the alcohol and can make the wine taste harsh.

Infuse the flavors: Once the sugar has dissolved and the liquid is warm, reduce the heat to the lowest setting. Let the mulled wine gently infuse for at least 15-20 minutes, or up to an hour for a more intense flavor. Stir occasionally.

Add optional spirits: If using, stir in the 60ml (1/4 cup) of brandy or spiced rum during the last 5-10 minutes of the infusion time. Heat through gently, again without boiling.

Strain and serve: Carefully ladle the mulled wine through a fine-mesh sieve into heatproof mugs or glasses. Discard the spices and orange. Alternatively, you can carefully remove the orange and spices with a slotted spoon before ladling.

Garnish and enjoy: Garnish each serving with a fresh orange slice or a cinnamon stick, if desired. Serve immediately and enjoy the festive aroma and warming taste.