Preheat your oven to 325°F. Then, thoroughly butter and flour your cake pans.
In a mixing bowl, whisk together the flour, baking powder and soda, salt, and cocoa powder. Set aside.
Cream together your room temperature butter and sugar on a medium speed for 4-5 minutes, until it's light and fluffy. Then, with the mixer running, add your eggs one at a time, and finish with the vanilla.
Add your watered-down one cup of coffee to the milk in a measuring cup with a pour spout. Let it cool slightly, if still hot.
In three different additions, alternate stirring in the liquid and the dry ingredients to the egg/butter mixture, starting with the flour. Mix gently after each "round" of liquid and dry are added.
Pour the batter evenly into the three prepared pans and bake for 35-40 minutes, testing with a toothpick for doneness.
Let the cakes cool in their pans for up to five minutes, but no longer. Carefully turn them out onto a wire cooling rack to finish cooling. Once the cakes have fully come to room temperature, wrap each individual layer in plastic wrap and freeze until you're ready to assemble your cake.