Spray the inside of a 10-inch round cake pan with baking spray and set aside. Preheat oven to 350 degrees F.
In the bowl of an electric mixer using the paddle attachment, cream the butter and sugar replacement until pale yellow in color.
In a small bowl, whisk the milk, egg substitute, and vanilla together.
In medium bowl, combine the flour, cocoa powder, baking soda, espresso, and salt.
With the mixer on low speed, alternate adding the dry and wet ingredients to the butter and sugar mixture, starting with the dry ingredients and ending with the dry ingredients. Scrape down the sides of the bowl occasionally to make sure all ingredients are well blended.
Pour batter into prepared pan and bake for 1 hour, or until a toothpick comes out clean when inserted in the center. Remove cake from oven and allow to cool for 10 minutes before removing from pan. Remove cake from pan and set aside to fully cool before frosting.
When cake is completely cool, frost as desired.
Using the paddle attachment of an electric mixer, cream together the cream cheese, baking sugar replacement, and light butter until fluffy.
In a small bowl, combine cocoa powder and espresso powder. Then slowly beat the cocoa powder mixture into the creamed cheese mixture.
Add vanilla and beat until well blended. Stir in buttermilk, 1 tablespoon at a time, until frosting is a spreadable consistency. Frost cake as desired.