Place flour on a surface, make a well, and work in butter and salt.
Gradually mix in iced water until the grainy dough is incorporated.
Roll dough into a ball, wrap in film, and refrigerate for 20 minutes.
Roll pastry into a 40x20cm rectangle on a floured surface.
Fold into thirds, then give the pastry a quarter-turn.
Roll into a 40x20cm rectangle again and fold into thirds.
Wrap the pastry and refrigerate for 30 minutes.
Perform two more rolling and folding turns for a total of four.
Wrap and refrigerate for at least 30 minutes before use.
Preheat the oven to 200°C.
Roll the pastry out to a 3mm thickness.
Cut out six 10cm discs and six small leaf shapes.
Place pastry on a moistened baking sheet and refrigerate for 20 minutes.
Prick the discs with a fork and score veins into the leaves.
Brush apple halves with butter and sprinkle with caster sugar.
Mix sultanas, brown sugar, spices, and butter, then spoon onto pastry.
Slice apples finely and layer over the sultana mixture.
Add pastry leaves to edges and brush with butter and sugar.
Bake for 15 minutes, sprinkle with sugar, and bake for 5 more minutes.
Transfer tartlets immediately to a wire rack.
Melt sugar and butter in a saucepan for the sauce.
Add double cream and simmer until the mixture thickens slightly.
Serve tartlets with a spoonful of warm caramel sauce.