Preheat the oven to 325 degrees F.
In the bowl of an electric mixer fitted with the paddle attachment, stir together the flour, sugar, cocoa powder, baking soda, baking powder, and salt on low speed until combined.
In another bowl, combine the buttermilk, oil, eggs, water, and vanilla.
With the mixer on low speed, slowly add the wet ingredients to the dry, scraping the bottom of the bowl with a spatula.
Pour the batter into the prepared pans (about 16 ounces in each pan), over the chocolate cookie crusts, and bake for 25 to 30 minutes or until a toothpick inserted in the center of the cake comes out with a few moist crumbs on it.
Remove the cake pans from the oven and let the layers cool in pans for 15 minutes before inverting onto cooling racks to cool completely.