Pour the clementine juice into a pan on a high heat to warm through – don’t let it boil. Add a little sugar to sweeten – not too much, you still want that zippy clementine flavour.
Peel the ginger and grate a tiny bit into the pan. Grate a bit more onto a chopping board, then squeeze it over the pan of juice so you get a few drips of ginger juice in there. Take the juice off the heat.
Sprinkle the gelatine over the juice, then whisk in quickly.
Arrange 6 small serving glasses on a tray. Peel the clementines, slice into thin rounds and put 2 in each glass. Sieve the juice mix into each glass, allow to cool, then refrigerate for about 3 hours, or until set.
To serve, mix the vanilla into the yoghurt and dollop a spoonful on top of each jelly, then grate or shave a few pretty bits of chocolate on top.