In a pot, heat the cream. Pour the warm cream over the chocolate. Add the glucose and blend with a stick blender. Allow to cool to 35°C. When cooled, blend in the butter with the stick blender. Allow to crystallise, and transfer to a piping bag with a round nozzle.
Make a stiff meringue. Beat the egg whites until stiff peaks form, adding the castor sugar slowly and finally, the vinegar.