1.Cut cake into 1cm-thick slices. Cut each slice, diagonally, making two triangular sections.
2.Place cake around inside edge of prepared pudding bowl (see note), making sure narrowest end of cake is in the base of bowl; fill any gaps with pieces of cake. Trim edge; reserve any cake pieces.
3.Combine brandy and maraschino in small jug. Carefully brush cake with brandy mixture.
4.Chop a third of the chocolate finely; reserve. Melt remaining chocolate.
5.Beat cream and sifted icing sugar in small bowl with electric mixer until firm peaks form; fold in nuts. Halve cream mixture. Fold chopped chocolate through one half; fold melted chocolate through remaining half.
6.Spoon chopped chocolate mixture evenly over entire cake surface, leaving a cavity in centre; spoon remaining chocolate mixture into cavity.
7.Arrange reserved cake pieces over filling; brush with any remaining brandy mixture. Cover; refrigerate overnight. (Can be made 2 days ahead to this stage.)
8.Turn carefully onto serving plate; remove muslin. Dust top with combined cocoa and extra icing sugar.
You will need a 1.25-litre (5 cup) pudding bowl with a layer of damp muslin.Note