500 gramme packet Pura
65 grammes caustic soda
250 ml spring water
10 ml essential oil of Lavender (or your choice, or omit)
Melt the Pura, then leave for about an hour, meanwhile dissolve
caustic soda (carefully) in the water, and also leave to get
cool. Pour the caustic solution into the fat, then whisk
thoroughly (ideally with a hand-held electric mixer or stick
blender) until it thickens and goes custardy, and a trail is left
on the top when you lift the stirring implement out. This is
known as trace. Then add your essential oil, if using, pour
everything into a lightly-greased plastic mould (a plastic
lunchbox is fine), and place in the airing-cupboard wrapped in a
towel. Leave for 24-48 hours, then freeze for 12 hours (optional,
but it makes it easier to unmould and I think gives a better
final texture to the finished soap), unmould, and when thawed,
cut into chunks/slices. Leave to air-dry for a couple of weeks
before using.