Use a 8 x 4 x 2 1/2" loaf pan, (4 cups) or any 6 cup loaf pan or fluted tube pan, greased and floured.
In a medium mixing bowl whisk together the cocoa and water until smooth.
Allow to cool to room temperature and lightly whisk in the vanilla and eggs.
In a large mixing bowl combine the remaining dry ingredients and mix on low speed for 30 seconds to blend.
Add 1/2 the chocolate mixture and the butter.
Mix on low speed until the dry ingredients are moistened.
Increase to medium speed and beat for 1 minute to develop the cake's structure. Scrape down the sides.
Gradually add the remaining chocolate mixture in 2 batches, beating 20 seconds after each addition to incorporate the ingredients and strengthen the structure. Scrape down the sides.
Scrape the batter into the prepared pan and smooth the surface with a spatula.
The batter will be almost 1/2 inch from the top of a 4-cup pan.
(if your pan is slightly smaller, use any excess batter for cupcakes.) Bake for 50 to 60 minutes, (40 to 50 minutes in a fluted tube pan) or until a wooden toothpick inserted in the center comes out clean.
Place loosely with buttered foil over the cake after 20 minutes to prevent over browning.
The cake should start to shrink away from the sides of the pan only after removal from the oven.
Let the cake cool in the pan on a rack for 10 minutes.
Loosen the sides with a metal spatula and invert onto a greased wire rack.
If baked in a loaf pan, to keep the bottom from splitting, reinvert so that the top is up and cool completely before wrapping airtight.
TOPPING: This is for extra moistness and gives a subtle coffee accent.
In a small pan, stir together 1/4 cup water and 2 Tbsp sugar.
Bring to a full rolling boil.
Cover and remove from heat. When cool, add 1 tbsp Kahlua.
When cake is baked, brush half the syrup onto the top.
Cool the cake 10 minutes and invert it onto a lightly greased rack.
Brush the bottom and sides with remaining syrup.
Reinvert onto rack, top side up, to finish cooling.