Put all the ingredient in heavy-based saucepan and add 1 litre of water. Slowly heat it up, occasionally stirring. When it reaches boiling point cook for 5 minutes, then turn off the heat and let it cool.
Add the liqueur, stir well.
Pour the syrup into the bottles through a sterilized funnel. Place the cinnamon sticks in the bottles, also the cloves & juniper berries, equally divided. Seal the bottles and store in a cool place for up to 2 months.
To make mulled wine: pour 450 ml syrup and 1 bottle of red wine in a saucepan, add a few slices of orange or mandarin, then heat it up gently - but do not boil. Enjoy!