For suet pastry, rub ingredients and a pinch of fine sea salt in a bowl with your fingertips until fine crumbs form, add 160ml cold water and knead on a floured surface until a smooth dough forms. Wrap in plastic wrap and refrigerate until firm (1 hour).
Preheat oven to 180C. Bring Calvados to the simmer in a saucepan over medium heat, add currants and set aside until cool (10-15 minutes). Core apples and cut into thin slices. Place into a large bowl, add sugar, lemon rind, spice and currant mixture, stir to combine and set aside.
For caramel custard, stir sugar and 60ml water in a saucepan over low heat until sugar dissolves (3-4 minutes), increase heat to high and cook until dark caramel (8-10 minutes), remove from heat, add cream and milk (be careful as hot caramel will spit) and stir to combine. Whisk yolks in a bowl, then pour cream mixture over yolk mixture, whisking to combine. Return to pan with vanilla bean and seeds and stir continuously over low heat until mixture coats the back of a spoon thickly (8-10 minutes). Strain through a fine sieve, cover closely and set aside to cool (30-40 minutes).
Roll out pastry to 5mm thick and cut out six 15cm rounds and six 8cm rounds. Press large pastry rounds into six buttered and floured 200ml ovenproof moulds, fill with apple mixture, top with a small pastry round and press edges to seal. Bake until golden (25-30 minutes), turn out onto plates and serve hot with caramel custard.