Make a flour mound on the work surface with a deep well in the centre.
Work butter and salt into the flour until combined with butter lumps still visible.
Gradually mix in iced water until the dough is just incorporated.
Roll dough into a ball, wrap in film, and chill for 20 minutes.
Roll into a 40cm x 20cm rectangle, fold in three, and turn 90 degrees.
Repeat the folding and turning process one more time.
Wrap the pastry and chill in the fridge for 30 minutes.
Roll into a 40cm x 20cm rectangle, fold in three, and turn again.
Repeat the fold and turn a final time to reach four turns total.
Wrap and refrigerate the pastry for at least 30 minutes.
Whisk egg yolks and 20g caster sugar together to a ribbon consistency.
Whisk in the flour until the mixture is smooth.
Boil milk, 40g sugar, and vanilla, then pour gradually onto the egg mixture while stirring.
Return to the pan, boil while whisking, simmer for 2 minutes, then transfer to a bowl.
Dust the custard with icing sugar and let it cool.
Preheat your oven to 180°C.
Roll pastry to 2mm thickness and cut out six 12cm discs.
Place discs on a damp parchment-lined sheet, chill for 20 minutes, then prick with a fork.
Spread the custard evenly over the discs, leaving a narrow border at the edges.
Arrange apple slices in a fan pattern over the custard on each disc.
Bake for 18 minutes, sprinkle with 60g sugar, and bake for 5 more minutes to caramelise.
Transfer tartlets to a wire rack immediately to cool.
Serve tartlets topped with fresh passion fruit pulp.