In the microwave oven, melt 28 g (1 oz) chocolate. Stir in the water until smooth. Fit a pastry bag with a 1.5-cm (1/2-inch) plain tip. Brush the inside of the bag with the chocolate mixture, forming large, well-spaced streaks. Add the meringue and form 24 mushroom caps and 24 stalks on the baking sheet (make the bases of the stalks wider so they can stand on their own).