Pre-heat the oven to 150 degrees.
Place the vanilla pod, seeds and milk in a saucepan and bring to the boil over a medium-high heat before lowering to a simmer for 3-4 minutes.
Meanwhile, whisk together the egg yolks and 60g of the caster sugar until thick and pale. Carefully pour the hot milk over the egg yolks, whisking at the same time until the mixture thickens. Strain into a heatproof jug.
Arrange the diced apple in the base of 8 mini terracotta ramekins (with a diameter of 5cm or so). Pour the custard mixture carefully into them so that it comes three-quarters of the way up the ramekins. Arrange the ramekins in a roasting tray lined with a kitchen towel.
Pour boiling water into the tin so that it comes about half the way up the ramekins. Bake in the oven for 30-35 minutes until just set and with a little wobble in the centres of them.
Remove from the roasting tray and allow them to cool to room temperature. Chill until you are ready to serve them.
When ready to serve, sprinkle the surface of the crème brulees with the remaining caster sugar and use a chef's blowtorch to caramelise the surface of the brulees so that they are golden brown. Allow the sugar to set and turn hard, then serve.
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