- 175g/6oz plain chocolate, broken into pieces
- 175g/6oz caster sugar
- 6 eggs, separated
- 2 level tbsp cocoa, sieved
- 300ml/10fl oz double cream
- 2 oranges, zest only, finely grated
- orange segments or slices, steeped in Grand Marnier
- icing sugar
- 33cm x 23cm (13in x 9in) Swiss roll tin
- Lightly grease Swiss roll tin and line with non-stick baking parchment, pushing it into the corners.
- Preheat the oven to 180C/350F/Gas 4.
- Melt the chocolate slowly in a bowl over a pan of hot water. Allow to cool slightly.
- Place the sugar and egg yolks in a bowl and whisk with an electric whisk on a high speed until light and creamy.
- Add the cooled chocolate and stir until evenly blended.
- Whisk the egg whites in a large mixing bowl until stiff but not dry.
- Stir a large spoonful of the egg whites into the chocolate mixture, mix gently and then fold in the remaining egg whites, then the cocoa.
- Pour into the prepared tin and gently level the surface.
- Bake in the preheated oven for about 20 minutes until firm to the touch.
- Remove the roulade from the oven, leave in the tin and place a cooling rack over the top of the cake, being careful not to touch the cake.
- Place a clean damp tea towel on top of the rack, and leave for several hours or overnight in a cool place – don't worry, it will sink slightly. (If the tea towel dries out, simply re-dampen it.)
- Whip the cream until it just holds its shape, and stir in the orange zest.
- Dust a large piece of non-stick baking parchment with icing sugar.
- Turn the roulade out onto the paper and peel off the lining paper.
- Trim the two long edges for a smarter finish (it also gives you a chance to taste the trimmings!).
- Spread with the whipped cream and roll up like a Swiss roll: starting with one of the short edges, roll tightly to start with and use the paper to help. Don't worry if it cracks – that is quite normal and part of its charm!
- Serve slices with orange segments and Grand Marnier.