Break the chocolate into pieces then melt in a bowl set over a pan of gently simmering water. Remove the bowl from the heat and leave to cool and thicken slightly.
To assemble: turn the jelly out onto a sheet of non-stick baking parchment. Cut 12 slices from the orange jelly using a 5cm/2in round cutter. sit one jelly disc on top of each sponge.
spoon the melted chocolate over the jelly discs. Using the tips of the tines of a fork or skewer, lightly press to create a criss-cross pattern on top of the chocolate, then leave to set.