Preheat the ovens.
Grease a muffin tray and dust with flour to be able to remove the tarts easily when baked.
In a bowl, combine the butter, caster sugar and ground almonds, then add the egg and the corn flour. Keep aside util needed.
Then, roll the puff pastry into a rectangle of approximately 2-3 mm thick. Cut the pastry into 9-12 strips of 12cm x 5 cm. place in the fridge to cool.
Slice the apples very thinly, leaving the skin on, and sprinkle lemon juice over the apple pieces to prevent them from discolouring.
Spread a thin layer of almond cream over each pastry pieces, then add the apple slices with the peel side facing out. Sprinkle with some cinnamon then fold the pastry in half to cover the apples, the top of the apple slices with the peel should still be visible.
Starting on one end, roll the pastry and apples to the other end of the pastry and transfer to the muffin tray.
Repeat with the other rectangles of puff pastry. Bake in the oven for 25 -35 minutes until golden brown.
Remove from the oven and serve warm or cold with freshly whipped cream.