⅔ cup caster sugar
½ cup plain flour
¼ cup Dutch cocoa powder
2 tbsp boiling water
200 g dark chocolate, chopped
50 g unsalted butter
2 eggs, separated
⅓ cup caster sugar
½ cup thickened cream, whipped to firm peak
- Grease a 26cm x 36cm Swiss roll pan. Line base and sides with baking paper, extending paper 5cm above pan edges.
- Grease a 12.5cm x 23cm loaf pan, 7.5cm deep (6-cup capacity). Line base and sides with baking paper, extending paper 3cm above pan edges.
- To make sponge, beat eggs and sugar in a small bowl of an electric mixer for about 8 minutes, or until pale and tripled in size.
- Sift flour and cocoa twice onto a sheet of baking paper. Sift again over egg mixture. Add boiling water. Use a balloon whisk to gently fold until combined. Pour into prepared Swiss roll pan. Spread into corners.
- Cook in a hot oven (200C) for about 8 to 10 minutes, or until sponge springs back when gently pressed. Cool in pan.
- To make mousse, stir chocolate and butter in a medium heatproof bowl, sitting over a saucepan of simmering water, until smooth. Cool slightly.
- Beat egg yolks and sugar in a small bowl of an electric mixer until pale and creamy. Transfer to a large bowl. Stir in chocolate mixture.
- Beat egg whites in same clean small bowl of an electric mixer until firm peaks form. Fold into chocolate mixture. Fold in cream.
- To assemble, use prepared loaf pan as a guide, cut pieces of sponge to fit base and sides. Reserve remaining sponge. Line pan with sponge pieces. Pour in mousse. Cut remaining sponge and place to cover mousse. Refrigerate, covered overnight.
- To serve, invert onto a serving plate. Cut into thick slices.