In the top of a double boiler, combine 1/2 cup butter, white sugar and cocoa powder. Stir occasionally until melted and smooth. Beat in the egg, stirring until thick, 2 to 3 minutes. Remove from heat and mix in the graham cracker crumbs, coconut and almonds (if you like). Press into the bottom of an ungreased 8x8 inch pan.
For the middle layer, cream together 1/2 cup butter, heavy cream and custard powder until light and fluffy. Mix in the confectioners' sugar until smooth. Spread over the bottom layer in the pan. Chill to set.
While the second layer is chilling, melt the semisweet chocolate and 2 teaspoons butter together in the microwave or over low heat. Spread over the chilled bars. Let the chocolate set before cutting into squares.