For the watermelon punch, cut the melon into a container. To do this, cut the bottom end slightly flat so that the melon has a firm base. Then use a small, pointed kitchen knife to cut off a “lid”. This looks especially pretty if you notch it in a jagged shape. Set the lid aside and save it.
Scoop out flesh with a baller or spoon and keep the balls in a separate bowl.
Mix the melon balls with the rum, sugar and wine and leave to infuse, covered with cling film, for about 2 hours in a cool place.
Then fill the mixture into the melon and pour the watermelon punch with sparkling wine.