Cook over medium heat until syrupy (about 30 minutes). Add one gallon of burgundy wine and hold at serving temperature. Float orange slices on top if desired. Serve in mugs.
TIP: I watched Alton Brown make mulled wine recently on The Food Network. He used a buffet sized coffee maker. Just put all of the mulling ingredients in the ground coffee container. Pour the water and wine into the reservoir and let it "perk" -- the pour spout makes it easy to serve. My daughter says they generally have these large cofffe makers at the thrift shops.