Mix all the ingredients together. Put wine, brandy, orange slices, cloves, cinnamon sticks, star anise, all-spice, cardamom, and sweetener in a big pot. Stir them together quickly.
Warm it up. Heat the mulled wine on medium-high until it's almost starting to bubble. Be careful not to let it boil too hard because we want to keep the alcohol in. Then, turn the heat down to low, cover the pot, and let it simmer for at least 15 minutes, but you can simmer it for as long as 3 hours if you like. Take out the bits. Use a special strainer with tiny holes to take out the orange slices, cloves, cinnamon sticks, and star anise. Taste the mulled wine and add more sweetener if you want it sweeter.
Time to enjoy! Pour the warm mulled wine into heatproof mugs, and if you like, add extra cranberries or sliced citrus on top to make it even more special.