Step by step recipe:

1. 10 min.
   After preparing 500 g Brioche dough, refridgerate for 1 or 2 hours or overnight, so that the dough becomes firm.
   
   Then roll out dough (sprinkle generously with flour) into a large rectangle about 1 cm or 0.5 inch thick.
2. 3 min.
   Put this rectangle on a bigger sheet of cooking parchment. If necessary, reshape your rectangle after this transfer operation.
3. 5 min.
   Spread a layer of 300 g Confectioner's custard (Crème pâtissière, or French pastry cream) all over dough rectangle, 0.5 cm or 0.25 inch thick (add more if you wish).
4. 5 min.
   Now your goal is to roll up the dough to form a cylinder.
   
   It looks difficult, but in fact it's quite easy, thanks to the paper sheet. Use it to start rolling, without touching the dough, and so form the roll.
5. 
   Continue until completely rolled up.
6. 2 hours
   Put roll on a baking sheet, and refrigerate for about 2 hours, until the roll becomes quite firm.
7. 3 min.
   After this time, remove roll from the fridge and with a large sharp knife, trimm off the ends to neaten.
   
   Note: you can cook these bits later.
8. 10 min.
   Then cut the roll into slices about 3 cm or 1.5 inches thick, and arrange them in a round mould or tray, touching one touching another.
   
   That's why firm dough is absolutely essential, otherwise the slices will squash during cutting.
9. 2 hours
   Cover mould with a plastic sheet, and leave in a warm place for 2 hours.
10. 3 min.
    After this time, preheat oven to 180°C or 356°F. Brush top of cake with 1 beaten egg yolk.
11. 40 min.
    Put in the oven for about 30 minutes.
12. 10 min.
    Turn out on a wire rack.
    
    When cake is cool, you can decorate it with 100 g fondant icing, melted in bain-marie or microwave oven.