Step by step recipe:

1. 3 min.

   Prepare the chestnut brioche dough

   Put into a food-mixer bowl: 200 g flour, 50 g chestnut flour (sieved), 10 g Vanilla sugar, 5 g fine (or table) salt, 10 g yeast, 50 g Soured dough (if possible) and 370 g egg.
2. 15 min.
   Knead for 15 minutes.
3. 2 min.
   Add 125 g butter and 20 g caster sugar.
4. 1 hour
   Continue kneading until the butter is fully mixed in.
   
   Gather the dough into a ball, wrap in plastic film and leave to rest for 1 hour at room temperature.
5. 12 hours
   After resting, press down on the dough (to expel gas), gather into a ball again, then wrap in plastic film and refrigerate overnight.
6. 5 min.

   Prepare the butterscotch apples

   Peel 2 apples, and cut small (dice, ideally).
7. 3 min.
   Melt 30 g Clarified butter in a frying pan on high heat, then add 50 g brown sugar.
8. 6 min.
   When the sugar begins to caramelize, add the apples all at once and sauté until well cooked and caramelized.
9. 3 min.

   Roll the brioche

   Take the brioche dough out of the fridge and dust with flour.
10. 5 min.
    Roll out into a strip the same width as the length of your loaf tin or mould, and about 60 cm (2 ft) long.
11. 
    Lay apple pieces in a row at the near end of the strip...
12. 
    ...and start rolling up, adding more rows of apples as you go.
13. 7 min.
    Finish by turning the "seam" to underneath.
    
    Trim the roll if necessary to fit your tin.
14. 1 hour 30 min.
    Sit the roll in the tin or mould and brush with beaten egg to glaze.
    
    Leave in a warm place to rest for 1 hour 30 minutes.
15. 2 min.
    After resting, glaze the brioche again.
    
    Preheat the oven to 360°F (180°C).
16. 1 min.
    If you wish, you can snip the top of the brioche with scisors to help it rise in the oven.
17. 30 min.
    Bake for about 30 minutes.
18. 
    Leave to cool on a wire rack.