Place egg whites in a large bowl; let stand at room temperature 30 minutes.
Preheat oven to 275°. Place confectioners' sugar, walnuts, cocoa and coffee in a food processor; process until finely ground and set aside.
Add salt to egg whites; beat on medium speed until soft peaks. Gradually add superfine sugar, 1 tablespoon at a time, beating on high after each addition until sugar is dissolved. Continue beating until stiff glossy peaks form. Carefully fold in walnut mixture until blended.
Pipe or drop by rounded teaspoonfuls 1 in. apart onto parchment paper-lined baking sheets. Air dry for 30 minutes before baking. Bake 18-20 minutes. Remove macaroons from baking sheet to a wire rack; cool completely. Remove from parchment; store in an airtight container.