Step #3 Coat 2 (9-inch) round cake pans with cooking spray; line bottoms of pans with wax paper.
Step #4 Lightly coat wax paper with cooking spray; dust pans with 1 tbsp flour; shake out any excess.
Step #5 Combine cocoa, 1/2 c boiling water, & 1 oz bittersweet chocolate in a small bowl, stirring until smooth; cool.
Step #6 Place 3/4 c granulated sugar, 1/2 c dark brown sugar, & 1/4 c butter In a large-ish bowl; beat with a mixer at medium speed 2 mins or until well mixed.
Step #7 Add egg substitute; beat well.
Step #8 Lightly spoon 2 c flour into dry measuring c; level with a knife.
Step #9 Combine flour, & salt, baking soda, stirring well with a whisk.