Nanaimo bars (canadian)

5 tb Cocoa
    1/2 c  butter
    1/4 c  White sugar
      1    Egg
    1/2 ts vanilla
      2 c  Graham wafer crumbs
           FILLING:
  1 1/4 c  Icing sugar
    1/2 c  butter
      3 tb Custard (Birds)
           Milk
           ICING:
      3    Squares semi-sweet chocolate
      2 tb butter
      2 dr vanilla
 
  In a large saucepan melt the butter and stir in the cocoa and sugar.
  Add 1 beaten egg with the vanilla to the melted butter. Add the 2
  cups of "Graham" wafers and mix well. Press this mixture into the
  bottom of a lightly greased 9*9 inch pan. Place in the refrigerator.
  FILLING: Beat together icing sugar, butter, and custard. Add a little
  milk if needed to make a smooth dough. Spread on first layer and
  return to the refrigerator.
  TOPPING: Melt chocolate, butter and vanilla in a saucepan. Work
  quickly to get a smooth even layer. Return to the refrigerator to
  set. Cut into bars. Refrigerate.