1 hr 15 min.
Preheat the oven to 170°C (150 fan) | 325°F | gas 3 and grease and line an 18 cm | 7" ? springform cake tin with greaseproof paper.
Melt together the chocolate, butter and sugar in a saucepan until smooth. Remove from the heat, allow to cool slightly, then stir in the brandy if using.
Beat the eggs in a large mixing bowl until smooth, then beat in the flour. Slowly beat the melted chocolate mixture into the eggs and flour until smooth.
Sit the lined cake tin in a large roasting tin and wrap a double layer of aluminium foil around the outside of the cake tin so that it comes up past the rim of the tin. Pour the chocolate batter into the tin and tap lightly on the side to release any trapped air bubbles. Pour boiling water into the roasting tin so that it comes about halfway up the side of the cake tin.
Bake in the oven for 40-50 minutes until just set; the tip of a knife will come out just clean when inserted about 3 inches from the edge of the cake. Remove from the oven and carefully lift out of the roasting tin. Allow to cool before turning out from the springform tin.
Carefully lift onto a presentation plate. Dust the cake liberally with the icing sugar and decorate with birthday candles before serving.