For the pears
2 large pears, peeled, cored and each sliced into 16 crescents
1 vanilla pod, split in half
2 heaped tbsp caster sugar
500ml (18fl oz) water
For the roulade
200g (7oz) dark chocolate (70% cocoa solids), broken into pieces
175g (6oz) caster sugar, plus extra for dusting
6 free-range medium eggs, separated
1 tsp ground ginger
For the filling
300ml (1/2 pint) double cream
1 tbsp icing sugar, sifted, plus extra for dusting
Preheat the oven to 180ºC/350˚F/Gas Mark 4. Line a 23x33cm (9x13in) Swiss roll tin with baking parchment. Place the pears, vanilla and sugar in a pan with the water. Simmer for 15 minutes until soft with a bit of a bite. Drain and cool.
Melt the chocolate in a heatproof bowl over, but not touching, a pan of barely simmering water. Set aside to cool slightly. In a large bowl, whisk the sugar (reserving 1 tablespoon) with the egg yolks until pale and doubled in volume. Stir in the chocolate and the ginger. In a new bowl, whisk the egg whites until they form stiff peaks and add the reserved sugar. Fold the egg whites into the chocolate and ginger mixture, place in the tin and bake for 15 minutes.
Let the roulade cool, covering with a damp tea towel to prevent cracking. To make the filling, whip the cream into soft peaks and fold in the icing sugar. Dust a sheet of baking parchment with caster sugar and turn the roulade out on to it. Peel off the baking parchment and spoon over the cream and scatter the pears. Use greaseproof paper to roll up the roulade, beginning from one short end. Dust with icing sugar and serve.