Heat oven to 190C/170C fan/gas 5.
Lightly oil and line a 23 x 32cm Swiss roll
tin with baking paper. Mix the coffee with
1 tbsp warm water. Beat the eggs, both
sugars and the coffee mix together in a
large mixing bowl with an electric whisk
for about 8 mins or until the mixture is
thick and airy like meringue and holds
a trail when you lift up the beaters.
Sift the flour and cocoa powder over
the fluffy egg mix, then fold in very gently
using a large metal spoon. Pour the
mixture evenly into the lined tin and
carefully tip it so it spreads evenly
without being deflated. Use a knife if
necessary to very gently tease it into the
corners. Bake for 12-15 mins or until the
cake feels spongy but firm when touched.
Lay a sheet of baking paper on the
work surface and sprinkle with a little
caster sugar. Tip the tin upside-down
onto the paper and let the cake fall out.
Carefully peel off the paper. Roll up the
cake lengthways from one of the short
ends with the help of the paper, rolling it
inside so the cake doesn’t stick. Cool.
The cake becomes even more moist
if left overnight wrapped up, then iced
the next day.
For the chocolate icing, put the
chopped chocolate in a medium bowl.
Heat a small pan of water (one-third full)
until boiling, remove it from the heat,
then sit the bowl of chocolate over the
top. Leave for a few mins off the heat
until melted. Remove the bowl from the
pan, then leave the chocolate until it is
cool to the touch. Beat the mascarpone
and quark together, then sift and stir in
the icing sugar and cocoa powder. Stir
in the cooled melted chocolate (keeping
a couple of tsp back for drizzling), then
the coffee mixed with the vanilla extract.
Carefully unroll the cake, don’t
worry if it cracks a bit, and discard the
paper. Spread half the icing over the
unrolled cake, then re-roll it, finishing
with the join underneath. Place the cake
on a serving plate. Swirl the rest of the
icing all over the cake to cover it, then
drizzle over the reserved melted
chocolate. Decorate with a sprig of holly.