Melt the chocolate with the butter in a bowl over a pan of simmering water (see
Beat the eggs and sugar until slightly thickened. Sift the flour over the mixture, then add the almonds and chocolate mixture and fold in until evenly combined.
Grease and line a 23 cm (9 inch) square cake tin. Turn the mixture into the tin and bake in a preheated oven, 160°C (325°F), Gas Mark 3, for about 35 minutes until just firm. Transfer to a wire rack to cool.
Heat the cream in a pan until almost boiling. Remove the pan from the heat and add the chocolate. Leave until the chocolate has melted, then stir until smooth. Transfer to a bowl and leave to cool until thickened.
Slice off the top of the cake if it has risen in the centre. Halve the cake horizontally and sandwich the halves with one-third of the chocolate cream. Spread the remainder over the top and sides of the cake, swirling it decoratively with a palette knife.