This is an interesting traditional alternative to mulled wine. Needs a little longer to prepare however - plan ahead. Note that due to the port, it's also more alcoholic than ordinary mulled wine - warn anyone driving.
Half a dozen ordinary oranges (Jaffa, Navelina, etc)
2 bottles red wine - quite heavy
1 bottle port
Some recipes I have seen call for Seville oranges (and no grapefruit) but we wanted this for Christmas/NY and it's too early for Sevilles.
Place the fruits in a baking dish, and bake in a medium oven until the skin of the fruit starts to brown. I found this took about 30-40 mins.
Allow the fruit to cool to handleable temperatures. Stab each with half a dozen cloves. Place the fruit in a deep dish add the sugar, pour on the two bottles of wine (NOT the port) and leave it to stand for a day.
Mash the fruit down into the wine. We found the grapefruit mashes easily, the oranges need cutting with a knife to facilitate this.
Pour off all the liquid through a sieve, discard the pulp. We found the sugar doesn't completely dissolve in the cold wine, so we scooped this into the final pot, with the liquid.
Add the bottle of port.
Heat. Do not allow it to boil, but bring it to the sort of temperature you'd expect from a cup of tea or coffee.