1. Preheat oven to 350°F
2. Coat 2 8-inch round cake pans with cooking spray.
3. Line bottom of each pan with waxed paper.
4. Combine cocoa, 3/4 cup boiling water, and butter, stirring with a whisk until blended. Cool.
5. Combine brown sugar and granulated sugar in a large bowl, stirring well until blended.
6. Add egg substitute; beat with a mixer 2 minutes or until light and creamy.
7. Add the cocoa mixture, and beat 1 minute.
8. Lightly spoon flour into dry measuring cups; level with a knife.
9. Combine flour, baking powder, baking soda, and salt.
10. Gradually add the flour mixture to the sugar mixture; beat 1 minute or until blended. Stir in vanilla extract.
11. Pour batter into prepared pans.
12. Bake for 28 minutes or until a toothpick inserted in the center comes out clean.
13. Cool in pans 10 minutes on a wire rack.
14. Remove from pans.
15. Wrap in plastic wrap, and freeze for 2 hours or until slightly frozen.
16. Spread ice cream in an 8-inch round cake pan lined with plastic wrap.
17. Cover and freeze 4 hours or until firm.
18. To assemble cake, place one cake layer, bottom side up, on a cake pedestal.
19. Remove ice cream layer from freezer; remove plastic wrap.
20. Place ice cream layer, bottom side up, on top of cake layer.
21. Top with remaining cake layer.
22. Combine whipped topping and peppermint extract, and stir until blended.
23. Spread frosting over top and sides of cake.
24. Sprinkle with crushed peppermints.
25. Freeze until ready to serve.
26. Let cake stand at room temperature 10 minutes before slicing.