Step 1: What you Need
2 bottles of tawny port (the cheap stuff is fine)
half liter of brandy
mulling spices: cinnamon, cardamom, and cloves
1 orange peel
10 sugar cubes
Step 2: Mulling the Port
Warm the mixture to right before boiling, and let it sit at low heat for an hour or so. It is important to not allow it to boil or bubble in any way, as that will burn off the alcohol.
Step 3: Set the Sugar on Fire!
Now for the fun part. Once your Glögg has steeped sufficiently, it's time to add the final ingredients: sugar and brandy. I use around 10 sugar cubes, which I find plenty sweet. Add more or less depending on your taste preferences.
Place a few sugar cubes on a metal grate or pan, and pour a heavy splash of brandy over them. Quickly light the sugar on fire, and ladle the port over the sugar until it is fully dissolved. If desired, add more brandy to taste.