In a saucepan, bring the water to a boil. Remove from the heat; stir in chocolate buttons until melted. Cool for 20 minutes.
Meanwhile, in a mixing bowl, cream butter and sugar. Add egg yolks; mix well. Beat in coating and vanilla. Combine flour and bicarb soda; add to creamed mixture alternately with buttermilk. Mix well. Stir in the coconut and pecans.
Beat egg whites until stiff peaks form; fold into the batter. Pour into three greased and floured 20cm square baking trays. Bake at 180 degrees C for 25-30 minutes or until cake tests done. Cool in trays 10 minutes; remove to wire rack to cool completely.
Combine icing ingredients in a mixing bowl; beat well. Ice tops of two layers; stack on serving plate with plain layer on top. Ice top and sides of cake.