1. Place the milk, water, salt, rice and sugar in a large saucepan, bring to the boil over medium heat then reduce the heat and simmer, uncovered, for 30 minutes stirring occasionally.
2. Add the lemon peel and continue to simmer, stirring occasionally, for another 30 minutes. The mixture should be thick enough to coat the back of a wooden spoon. If it isn't, continue simmering for a further 5 to 10 minutes. Remove from the heat.
3. In a medium sized mixing bowl, beat the egg well then add a few spoonfuls of the rice mixture to the beaten egg and blend thoroughly. Repeat a couple times, then add the diluted egg mixture to the rice mixture and stir well. Return to a low heat for a 2-3 minutes, stirring constantly.
4. Transfer to individual serving dishes and sprinkle with cinnamon. Chill for at least 1 hour. Serve cold.