For the rice pudding, place the rice in a medium saucepan, cover with cold water and bring to a boil, stirring constantly.
Once it has come to the boil, drain then return the rice to the pot and add 1.5L of the milk, mandarin zest, vanilla seeds and pod and the caster sugar.
Cook over medium/high heat for 20-25 minutes, stirring often and bringing it to a boil. Once it boils, turn the heat to low and add the cream, stirring for another 5-10 minutes. You want thick but not stodgy consistency. Use the extra milk to lighten if needed.
While the rice pudding cooks, place a medium saucepan over medium-high heat and add half the sugar. Gently swirl this around as it melts and begins to caramelise, then continue to add in the sugar a little at a time and swirl it through to create a dark caramel.
Add the mandarins to the caramel with the juice of 1 mandarin and gently stir through for 2 minutes, over the heat, to create a caramel sauce and softened mandarins.
Serve the rice pudding, hot, topped with mandarins and caramel.