Decadent chocolate tart

Lightly grease a 1 kg loaf tin with butter or non-stick spray. Line with baking paper and grease again.
Heat the butter and sugar in a saucepan until the butter has melted.
Remove from the heat and add the crushed biscuits. Mix and leave to cool.
Press half the mixture onto the base of the loaf tin and chill.
Dissolve the cocoa powder in the water and fold into the cream. Stir in the brandy.
Beat the egg white until stiff and fold into the cream mixture.
Pour the mixture over the crumb base spreading evenly. Sprinkle with the remaining crumb mixture.
Cover and freeze for at least 2 to 3 hours (preferably overnight) or until hard.
Turn out and serve with chocolate sauce.