In a heavy saucepan, combine the chocolate and butter. Cook over low heat, stirring constantly, until smooth. Preheat and grease waffle iron.
In a medium bowl, beat together the eggs, sugar and vanilla until light. Stir in the chocolate mixture, then gradually stir in the flour until smooth.
Drop batter by heaping spoonfuls onto the preheated waffle iron to make four cookies at one time. Close waffle iron and cook for 60 to 90 seconds, or until cookies are firm. Remove from iron to cool on wire racks. Dust with confectioners' sugar when cool.