Combine butter, sugar, cocoa and egg in a saucepan.
Place over simmering water in a double boiler, or over
low direct heat. Cook and stir until thick and smooth,
about 5 minutes.
from heat and stir in vanilla.
graham wafer crumbs, coconut and nuts and stir to combine.
in a greased 9 inch square pan and pack down firmly.
Cream butter. Combine milk and custard powder and blend
until smooth. Stir into the butter.
icing sugar and blend on low speed with mixer until
smooth. Stir in vanilla.
filling over chocolate layer. Chill for 15 minutes.
Melt chocolate and butter together. Spread over the
filling. Refrigerate. Cut into bars.