Preheat the oven to 350F. Butter 2 round cake pans (9-inch ones) and line with parchment paper.
Mix together the flour, cocoa powder, baking soda, baking powder, coffee and salt in a bowl. Set aside.
Add the eggs, mayonnaise, sugar, water and vanilla into the flour mixture. Stir until well-blended but do not overmix.
Fold in the chocolate chips. Transfer the batter to the prepared pans.
Bake in the preheated oven for 20-23 minutes or until a toothpick inserted in the center comes out clean. Oven temperatures vary so adjust the time accordingly.
Cool the cakes in the pans for 10 minutes and then transfer to a wire rack. Cool the cakes completely before adding the chocolate filling and coating with the frosting.