Preheat oven to 350.
Butter and flour two 8-inch cake pans or springform pans; set aside.
In a large mixing bowl sift together flour, baking soda, salt, and cocoa.
Stir in sugar; set aside.
In a separate bowl whisk together mayonnaise, eggs, vanilla, kahlua, and water.
Pour mayonnaise mixture into flour mixture and stir together until just combined.
Divide batter evenly into prepared cake pans.
Bake for 40 to 45 minutes, or until toothpick inserted in the center of the cakes comes out clean.
In the meantime, prepare frosting.
In your mixer's bowl combine chilled heavy cream, sugar, cocoa, and kahlua.
Beat mixture until stiff peaks form.