Step by step recipe:

1. 15 min.
   Peel 8 apples, and cut in half across.
2. 5 min.
   Remove cores, no matter if the apples break during this operation.
3. 5 min.
   Cut each half apple in half again.
4. 30 min.
   Melt 30 g butter in a large pan or frying pan. Then sprinkle with 50 g caster sugar and put apples on top. Allow to caramelise on low heat.
5. 3 min.
   Meanwhile, spread out the first circle of puff patry (this will be the pie base), prick it with a fork or a pique-vite. Put back in the fridge.
6. 3 min.
   Spead out the second puff pastry circle (pie lid) and make a small hole in the centre to allow steam to escape during cooking (the "chimney").
   
   Put back in the fridge.
7. 
   Apples will be caramelized after about 30 minutes.
8. 10 min.
   Take out the pie base, place on work surface and spread the apples over, caramel side upwards and packed well towards the centre, to within about 1 cm - ½ inch of edge.
9. 3 min.
   With a brush, moisten edge of pastry with cold water.
10. 5 min.
    Place the second pastry circle on top.
11. 5 min.
    Press all around the edge to seal.
12. 3 min.
    If necessary cut round...
13. 
    ...and trim off any excess.
14. 3 min.
    Glaze top with beaten egg-yolk.
15. 25 min.
    Leave in the fridge while oven preheats to 210°C or 410°F.
    
    Put in the oven for about 25 minutes.
16. 
    Watch the coloration: as soon as it looks like the photo, it's done.
17. 
    Serve warm if possible.