Put the watermelon into a heavy-based
saucepan over a low heat, cook gently until it softens.
In a separate saucepan, dissolve the
sugar in the water and add the cinnamon sticks.
Bring to the boil and cook for 5
minutes, then remove from the heat.
Cover the pan and leave the syrup to
cool and infuse.
Strain the syrup into the watermelon
puree and stir in the lime juice.
Pour the mixture into a freezer
container, cover and freeze for 2 hours, removing it at 30 minute
intervals and beating it with a fork to ensure no ice crystals form.
Beat the egg white until stiff and add
it to the mixture, blending it in thoroughly.
Freeze for a further 60 minutes,
beating once with a fork after 30 minutes.
Transfer the mixture to the
refrigerator 30 minutes before serving.
