Preheat oven to 110 C / Gas 1/4. Line two baking trays with foil.
Beat egg whites until fluffy. Add salt and cream of tartar; continue to beat. Gradually add the sugar and beat for 6-7 minutes or until stiff, smooth and glossy. Beat in vanilla extract and grated chocolate (or instant espresso).
Transfer mixture into a piping bag. Pipe neat mounds onto baking trays, leaving room for them to spread a little. Bake for 1 hour or until the meringues are dry but not brown.
Remove from oven and let cool briefly. Carefully transfer meringues from the foil to a wire rack. Let cool fully.