1. Preheat oven to 350°.
2. To prepare cake, coat 2 (9-inch) round cake pans with cooking spray; line bottom with wax paper. Coat wax paper with cooking spray.
3. Combine cocoa, 1/2 cup boiling water, and chocolate in a small bowl, stirring until smooth. Cool.
4. Place granulated sugar, brown sugar, and 1/4 cup butter in a large bowl; beat with a mixer at medium speed until well blended (about 2 minutes). Add egg substitute; beat well.
5. Weigh or lightly spoon flour into dry measuring cups; level with a knife. Combine flour, baking soda, and salt, stirring with a whisk. Combine buttermilk, sour cream, and vanilla. Add flour mixture and buttermilk mixture alternately to sugar mixture, beginning and ending with flour mixture. Add cocoa mixture; beat well.
6. Pour batter into prepared pans; sharply tap pans once on counter to remove air bubbles. Bake at 350° for 25 minutes or until a wooden pick inserted in center comes out clean. Cool in pans 10 minutes on a wire rack; remove from pans. Cool completely on wire rack.
7. To prepare frosting, combine powdered sugar, cream cheese, coffee, and 1 tablespoon butter in a large bowl. Beat with a mixer at medium speed until smooth (do not overbeat).
8. Place one cake layer on a plate. Spread half of frosting on top; sprinkle with 1/3 cup brickle chips. Top with remaining cake layer. Spread remaining frosting over top layer; sprinkle with remaining brickle chips.