Chilled, caramelised oranges with Greek yoghurt

Using a small, sharp knife, cut a thin slice off the top and bottom of the oranges, and then slice skin off vertically, turning the orange as you go, being careful to keep as mush flesh as possible, but removing all the pith.
Slice each orange into 5 mm rounds, trying to reserve as much juice as you can.
Put the slices, pouring the juices as you go, into a bowl as you cut them.
To make the caramel, put the castor sugar, water and cardamom pods into a large saucepan and swirl (not stir) a little to dissolve the sugar.
Slowly bring to the boil without stirring, until the syrup becomes a dark amber colour.
Take the saucepan off the heat and tip the oranges and the juice into it.
Quickly coat the orange slices in the caramel and then pour onto a flat plate. Do this quickly, or the caramel will set before you can get it out of the saucepan.
If you can pick out the cardamom pods without burning your fingers, great, but there is no need to do it yourself: let those eating do a little work as well.
Let the oranges cool, then put them in the fridge to chill for a while.
Put the Greek yoghurt on the table so people can help themselves.