Line a 15x10-inch jelly roll pan with waxed paper. Grease and flour lined pan; tap out excess.
In a medium bowl, combine flour, cocoa powder, cornstarch, baking soda, baking powder, and salt. Mix well.
In a separate bowl, using an electric mixer, beat egg yolks and 1/4 cup sugar until fluffy. In a small bowl, using CLEAN beaters, beat egg whites on high until foamy. Gradually add 1/2 cup sugar, beating until stiff, but not dry, peaks form.
Fold 1/3 beaten egg whites into egg yolk mixture. Alternately fold in remaining whites and flour mixture.
Pour batter into pan; smooth top. Bake until a toothpick inserted in center comes out clean, about 14 minutes.
Dust a clean cloth with remaining sugar.
Turn cake out onto prepared cloth; remove waxed paper. Trim cake's edges.
Starting with a long side, tightly roll up cake WITH CLOTH!
Transfer cake, seam-side down, to a wire rack to cool. Unroll cake; remove cloth.
Mix whipped topping and chocolate chips together and spread over cake to within 1/2 inch of edges.
Re-roll cake; place seam-side down on a plate. Refrigerate.