Chocolate brown log

Preparation time: 50 minutes, Cooking time: 12 minutes for the biscuit; Serves 4

Ingredients for the chocolate & chestnut ganache montée
50 g milk chocolate  
45 g 30% single cream (1) 
120 g chilled 30% single cream (2) 
40 g chestnut cream 

Ingredients for the chocolate cookie roll
100 g flour  
4 eggs  
80 g sugar  
1 sachet vanilla sugar  
15 g cocoa powder  
1 pinch of Le Paludier de Guérande Fleur de sel

Ingredients for the whipped cream
150 g full-fat cream 
1 tablespoon mascarpone 
1 tablespoon powdered sugar 
1 vanilla pod 

Ingredients for the caramel
90 g sugar 
10 cl liquid cream  
35 g soft butter 
1 pinch of Le Paludier de Guérande Fleur de sel 

Brown chocolate ganache: (prepare the day before or a few hours in advance). 
Bring the small amount of cream (1) to the boil.  
Pour over the crushed chocolate in three batches, stirring well each time.  
Once the mixture is smooth, add the other part of the cream (2) and the chestnut cream.   
Mix and set aside in the fridge for at least 3 hours. 

The cookie roll:  
Whisk together egg yolks, powdered sugar, vanilla sugar and cocoa.  
Add sifted flour.  
Beat egg whites until stiff with a pinch of salt.  
Gently fold into the egg yolks in batches, using a pastry blender.  
Pour onto baking paper and spread with a spatula.  
Bake for 12 to 15 minutes at 180°C.  
Once out of the oven, turn the cookie out onto a kitchen towel or baking paper to loosen the baking paper.  
Leave to cool with a tea towel over it so that the cookie doesn't dry out.  

Chantilly cream :  
Pour the very cold liquid cream, mascarpone, powdered sugar and scraped vanilla pod into the bowl of a cold mixer.  
Whip the cream until stiff.  
Set aside in a piping bag.  

For the caramel :  
Pour the sugar into a saucepan and cook over medium heat until the caramel has a nice brown color.  
Meanwhile, heat the cream.  
Off the heat, add the hot cream to the caramel, stirring constantly. 
Add the cubes of soft butter a little at a time.