Put the milk, rind, cinnamon sticks and half the sugar in a saucepan and heat to just below boiling. Set aside for 10 minutes.

Using a wire whisk, combine the yolks, remaining sugar and ground cinnamon in boel until thick and pale. Pour in the milk in a steady stream, whisking constantly.

Wash the pan, pour in the mixture and stir over very low heat for 5-10 minutes, until thickened. To test, run a finger through the mixture across the back of a wooden spoon. If it leaves a clear line, the custard is ready. Strain it into a bowl and leave to cool to room temperature. Pour it into a 1.25 litre shallow metal container. Freeze for 2 hours, or until firm.

When half frozen around the edges, beat well then freeze again. Repeat the beating and freezing process twice more