If sheep's milk yoghurt is unavailable, any thick natural yoghurt can be used. Chilling overnight will make it easier to unmould this jelly. You'll need to start this recipe a day ahead.
Note Choose a silicone bundt mould or one made from a single piece of metal as joins in metal moulds may cause jelly to leak. Test for water tightness beforehand. Alternatively, use any mould of a similar capacity or even divide mix among individual moulds.