1. For bottom Layer: Melt unsalted butter, sugar and cocoa in top of a double boiler. Add egg and stir to cook and thicken. Remove from heat. Stir in crumbs, nuts and coconut. Press firmly into an ungreased 8 by 8 inch pan.
2. For Middle Layer: Cream butter, cream, custard powder, and icing sugar together well. Beat until light in colour. Spread over bottom layer.
3. For Top Layer: Melt chocolate and unsalted butter over low heat. Cool. Once cool, pour over middle layer and chill.