Method
1
Preheat the oven to 180°C.
2
Line a 25 by 38 cm rimmed baking tray with parchment paper.
3
Whisk the eggs and granulated sugar until thick and pale.
4
Stir half of the vanilla into the egg mixture.
5
Sift the flour, cocoa powder, and salt into a bowl.
6
Fold the dry ingredients into the egg mixture.
7
Spread the batter evenly in the prepared tray.
8
Bake the sponge for 10 to 12 minutes.
9
Lay a clean kitchen towel on the counter.
10
Dust the towel generously with icing sugar.
11
Turn the hot sponge onto the towel.
12
Peel the parchment paper off the sponge.
13
Roll the sponge up in the towel from a short end.
14
Cool the rolled sponge completely.
15
Beat the chestnut puree, mascarpone, icing sugar, and remaining vanilla until smooth.
16
Whip the chilled heavy cream until it forms stiff peaks.
17
Fold the whipped cream into the chestnut mixture.
18
Unroll the cooled sponge carefully.
19
Spread the chestnut cream evenly over the sponge.
20
Roll the sponge back up without the towel.
21
Place the log seam-side down on a serving platter.
22
Chill the log for 30 minutes.
23
Place the chopped chocolate in a heatproof bowl.
24
Heat the remaining heavy cream until steaming.
25
Pour the hot cream over the chocolate.
26
Let the mixture stand for 2 minutes.
27
Stir the chocolate mixture until smooth.
28
Cool the ganache until spreadable.
29
Spread the ganache over the log.
30
Drag a fork through the ganache to make bark-like lines.
31
Chill the log until the ganache is set.
32
Dust the log lightly with icing sugar.
33
Arrange fresh cranberries around the log before serving.