Sift the cocoa powder through the finest strainer you have, to eliminate any lumps. Thoroughly combine it with 1/4 cup of the sugar. Set aside.
Pour the egg whites into a clean, dry bowl. Begin by whipping them with a mixer set on medium speed.
Add the salt and allow the egg whites to whip until they are whip, opaque and begin to hold a soft peak, 2 or 3 minutes. Increase the speed to high and pour in the remaining sugar (1 cup) in a very slow stream. This should take about 2 minutes.
The egg whites should retain a dull appearance. If they become shiny, you are adding the sugar too quickly, it is melting fast and the meringue is losing air. By the time you have added the sugar (1 cup), the egg whites should be very stiff, but not dry and separated.
With a rubber spatula, fold in the sugar and cocoa mixture, scattering it over the egg whites in three or four additions. Fold quickly but gently to retain as much air as possible.
Proceed immediately to the piping or shaping of the meringue before it has a chance to lose air from standing.
Bake for 30 minutes. The meringue needs to set quickly before the fat in the cocoa breaks down the meringue, making it fall. Rotate the pan so it bakes evenly.