Peel, core and slice the apples into a saucepan, add 3 tablespoons water and the vanilla pod, cover and cook very gently until the apples are soft. Then turn off the heat under the pan and remove the vanilla pod (which can be rinsed, dried and used again).
Now add the butter and apricot jam to the pan and, after a minute or two, beat the mixture to a puree. Taste and add a bit more sugar if you think it needs it. Now spread the apple pulp in a heatproof bowl, cover and chill in the fridge.
To make the caramel, simply put the sugar in a saucepan and heat until it starts to dissolve around the edge and darken. Shake the pan gently and continue heating, stirring once or twice with a wooden spoon; continue to cook until the syrup formed is a shade darker than golden syrup. Now pour immediately over the apples and chill again until firm and cold. Tap the caramel surface all over with a spoon to break it up before serving - and some chilled 'real' custard would be lovely with it.