Preheat oven to 350°.
Beat egg whites in a large bowl with a mixer at high speed until soft peaks form. Gradually add granulated sugar, beating until stiff peaks form.
Combine powdered sugar, cocoa, and candy bars in a small bowl, and mix well. Fold half of cocoa mixture into egg whites (egg whites will deflate quickly). Fold in remaining cocoa mixture until smooth. Drop the egg mixture by rounded tablespoonfuls onto baking sheet coated with cooking spray. Bake at 350° for 15 minutes (puffs will be soft in center).