Butter and flour 2 - 9 inch cake pans or 1 - 9x13 sheet pan. Whisk together flour, cocoa powder, espresso powder, salt and baking soda for about 2 minutes in small bowl. Cream together margarine and sugar until light and fluffy. Add eggs one at a time. Add vanilla and mayonnaise. Add flour mixture alternately with milk. With last addition, just mix until incorporated. Do not over mix. Pour equally into prepared pans and bake at 350 degrees for 35-40 minutes or until toothpick inserted in center of layer comes out clean. Cool on wire rack.
For frosting: Cream cream cheese and butter until well mixed. Add 1/2 of the powdered sugar, vanilla, cocoa powder, espresso powder and milk or half & half. Mix until smooth. Add remaining powdered sugar and beat until shiny. If too thick, add some more milk or cream. Generously frost first layer. Add second layer. Frost top and sides.