Pour 250 ml of boiling water over the tea bag in a cup and let it steep for 2-3 minutes. Remove the tea bag and let the tea cool down completely.
Puree the currants in a blender or with the blender. Strain the puree through a sieve and refine with the elderflower syrup. Stir the mixture into the cold tea.
To serve, fill a glass with ice cubes, pour the tea mixture over it and decorate with the currants on a stick.