INGREDIENTS (Serves 10-12)
For the chocolate sponge
4 large eggs
100 g (4 oz) caster sugar
65 g (2½ oz) self-raising flour
40 g (1½ oz) cocoa powder
For the icing and topping
275 g (10 oz) Bournville chocolate, broken into small pieces
450 ml (¾pt) double cream
4 tbsp apricot jam
Icing sugar, for dusting
Preheat the oven to 200°C/fan 180°C/gas 6. Lightly grease and line a 33 cm x 23 cm (13in x 9in) Swiss roll tin. Whisk the eggs and sugar in a large bowl until the mixture is pale, light and frothy. Sift in the flour and cocoa powder and carefully cut and fold together, using a metal spoon, until everything is incorporated, being careful not to beat out the air from the mixture.
Pour into the tin and spread evenly into the corners. Bake in the middle of the oven for 8-10 minutes until pale golden and the sides are shrinking away from the edge of the tin. Place a piece of baking parchment larger than the Swiss roll on the work surface, invert the cake onto it and remove the lining paper on top.
Trim the edges of the cake with a knife and make a score mark 2.5 cm (1in) in along the longer edge so it’s easier to roll. Roll up the cake from the scored edge using the parchment, rolling the parchment inside. Set aside to cool.
While the cake is cooling, make the icing. Melt the chocolate and 300 ml (½ pt) of the cream in a bowl over a pan of simmering water until completely melted (be careful not to overheat; the bowl must not touch the water). Refrigerate to cool and firm up (this icing needs to be very thick for piping). Whip the remaining cream.
Uncurl the cold Swiss roll and remove the paper. Spread a third of the icing over the surface, then spread the whipped cream on top, and re-roll tightly. Cut a quarter of the cake off from one end on the diagonal. Transfer the large piece of cake to a serving plate and angle the smaller cake to the side of the larger one to make a branch.
Cover the surface of the cake with the melted apricot jam. Place the remaining icing into a piping bag fitted with a star nozzle and pipe long, thick lines along the cake, covering it completely so that it looks like tree bark. Cover each end with icing (optional).
Finally, dust the cake lightly with icing sugar and garnish with fresh holly, to serve.