PLACE sugar, cocoa mix and butter in top of double boiler that is set over gently boiling water. Stir frequently until melted and smooth paste forms. Add morsels; stir. When morsels begin to melt, slowly stir in 1/2 cup evaporated milk. Stir until smooth and velvety. Cool to room temperature.
PLACE chocolate mixture, remaining evaporated milk and ice in blender (in batches, if necessary); cover. Blend until smooth. Pour into individual glasses or bowls. Top each serving with a dollop of whipped cream. Sprinkle with additional chopped morsels, if desired. Serve with a straw and/or spoon.