Prepare the frozen hand at least a day in advance. Wash and rinse the outside of a large disposable glove. Turn glove inside out and set aside.
Soak the gelatine leaves in cold water for 5 minutes. Remove the leaves, squeezing out excess water, and place in a small saucepan over low heat. Let the gelatine melt slowly, stirring occasionally. Once liquid, remove from the heat and combine with the 600ml water.
Carefully pour the gelatine mixture into the glove, using a funnel to help, if needed. You can also place the glove in a large glass or jar and stretch the end of the glove over the edge of the glass. Ensure that the liquid has completely filled all of the fingers, then tie the top closed. Place on a plate or tray lined with greaseproof paper and freeze for 1 to 2 days.
To make the ginger syrup:
Combine all syrup ingredients in a small saucepan. Bring to the boil, then reduce heat and simmer for 15 minutes. Remove from the heat, pass through a sieve to catch the ginger pieces and spices, then let cool.
To make the punch:
In a large punch bowl, combine the juice, sparkling water and alcohol, if using. Add half of the ginger syrup and stir well. Taste, then add more syrup to your liking.
Remove the hand from the freezer and dip briefly in warm water. Cut off the top, then carefully peel away the glove. Immerse the frozen hand in the punch and serve!