6eggs165 gm (¾ cup)caster sugar120 gmplain flour, sieved50 gmalmonds, finely ground in a food processor100 gmbutter, melted and cooledFor brushing:chocolate liqueurFor dusting:Dutch-process cocoaWhite chocolate mousse300 gmcouverture white chocolate, finely chopped40 mlmilk40 mlchocolate liqueur1gelatine leaf (titanium strength), softened in cold water for 5 minutes3eggs, separated350 mlpouring cream, whisked to soft peaksBitter chocolate glaze220 gm (1 cup)caster sugar160 gmdark chocolate (70% cocoa solids), finely chopped30 mlchocolate liqueur
Preheat oven to 180C. Whisk eggs and sugar in an electric mixer until pale and tripled in volume (6-8 minutes). Sieve over flour, in two batches, and fold in with a large metal spoon, then fold in ground almonds. Fold in butter. Spread one-quarter of mixture into a 23cm-diameter round on an oven tray lined with baking paper, repeat with remaining mixture and bake in batches, swapping trays partway through cooking, until light golden and centres spring back when lightly pressed (6-8 minutes). Cool completely on trays then remove baking paper.
Meanwhile, for white chocolate mousse, combine chocolate, milk and liqueur in a heatproof bowl placed over a saucepan of simmering water, stir occasionally until smooth (3-4 minutes). Squeeze excess water from gelatine, add to chocolate mixture, stir until dissolved. Remove from heat, cool for 5 minutes then stir in egg yolks and fold in whipped cream. Meanwhile, whisk eggwhites and a pinch of salt in an electric mixer until firm peaks form (2-3 minutes), fold into chocolate mixture and refrigerate until beginning to set (1-2 hours).
Place a 22cm-diameter, 10cm-high ring mould or the ring of a springform tin (don’t use base) on a tray lined with baking paper. Place a cake round in the base, trimming to fit snugly, then brush generously with liqueur. Spread with one-third of the white chocolate mousse, smoothing top, then dust heavily with cocoa. Repeat with remaining cake rounds, liqueur, mousse and cocoa, finishing with a layer of cake. Refrigerate until set (3-4 hours).
For bitter chocolate glaze, combine sugar and 60ml water in a small saucepan and stir over medium-high heat until sugar dissolves. Bring to the boil and cook without stirring until dark caramel (5-6 minutes), remove from heat and add 100ml water (be careful, hot caramel may spit). Return to heat, add chocolate and liqueur, stir until smooth then cool to room temperature.
To serve, run a hot knife around ring mould to loosen cake, place on a serving plate. Drizzle glaze over and serve immediately.