- Butter or margarine, for greasing
- 4 large eggs
- 150g caster sugar
- 65g self-raising flour
- 30g cocoa powder
- For the filling
- 300ml double cream
- 2 tbsp icing sugar
- For the ganache
- 200g dark chocolate, chopped
- 160ml double cream
- Icing sugar, for dusting
- You’ll need
- Silicone Swiss roll tray
Preheat the oven to 200C/180C fan/gas mark 6. Grease a silicone Swiss roll tray with butter or margarine and line with baking paper.
To make the sponge, in a bowl beat the eggs and sugar together until thick and creamy. Gently fold in the flour and cocoa powder, taking care not to lose the air from the mixture.
Pour the mixture into the Swiss roll tray, smoothing it out into the corners. Bake in the oven for 12–15 minutes until the sponge is springy.
Turn out the sponge onto a large piece of baking paper and while it is still warm roll into a log, keeping the baking paper inside with the sponge to prevent it sticking as it cools. Set aside to cool.
While the sponge cools, whip the double cream and icing sugar in a bowl to make the filling. Unroll the sponge and spread the whipped cream over the surface. Roll into a log again, without the baking paper inside this time, but using it on the outside to help you roll it tightly.
Grate the dark chocolate into a heatproof bowl. Warm the double cream and pour it over the chocolate. Gently stir until combined. Cover and cool in the fridge until the mixture is thick enough to spread.
Place the sponge log on a serving board and cover with the ganache. Roughly score the topping with a knife or corn skewer to make it look like bark, and leave to set for 15 minutes. Dust with icing sugar and serve, or keep for up to one week in an airtight container.