For the rough puff pastry, put the flour in a mound on the work surface and make a well in the centre. Place the butter and salt in the well and work them together with the fingertips of one hand, gradually drawing the flour into the centre with the other hand.
When the cubes of butter have become small pieces and the dough is grainy, gradually add the iced water and mix until it is all incorporated, but don’t overwork the dough.
Roll it into a ball, wrap in cling film and refrigerate for 20 minutes.
Flour the work surface and roll out the pastry into a 40x20cm/16x8in rectangle. Fold it into three, by folding the outside third on each side over onto the middle section, then give it a quarter-turn.
Roll the block of pastry into a 40 x 20cm rectangle as before, and fold it into three again. These are the first two turns. Wrap the block in cling film and refrigerate it for 30 minutes.
Give the chilled pastry another two turns, rolling and folding as before. This makes a total of four turns, and the pastry is now ready. Wrap it in cling film and refrigerate for at least 30 minutes before using.
For the tartlets, preheat the oven to 200C/400F/Gas 6.
On a light floured surface, roll out the pastry to a 3mm/1/8in thickness. Using a 10cm/4in pastry cutter, cut out six discs and six small leaf shapes.
Brush a baking sheet with a little cold water and lift the pastry onto it with a palette knife. Refrigerate for 20 minutes.
Prick the pastry discs with a fork, and mark the leaves with a knife to form veins.
Brush the halved apples with butter then sprinkle with some of the caster sugar and set aside.
Mix the sultanas with the soft dark brown sugar, spices and remaining butter in a bowl, then spoon the sultana mix onto the centre of the pastry.
Finely slice the apples, keeping them in their original shape, then place over the top of the sultana mix on the pastry and press gently to one side so the slices just separate, but the filling is enclosed.
Place the leaf shapes onto the edge of the pastry and brush with butter and sugar. (Place into the freezer at this stage if you want to and freeze until needed.)
Bake for 15 minutes, then sprinkle generously with the caster sugar and cook for another five minutes. Take the tartlets out of the oven and immediately lift them onto a wire rack with a palette knife.
For the caramel sauce, heat the sugar and butter in a small saucepan until melted and well combined. Pour in the double cream and simmer gently for 3-5 minutes, or until the mixture thickens slightly.
To serve, slide the tart onto a plate and serve with a spoonful of caramel sauce.