Step 1

Preheat the oven to 350°F and lightly coat a 13X9" pan with nonstick baking spray with flour.

Step 2

In a large bowl, whisk together the flour, baking powder, baking soda, salt, and sugar.

Step 3

In a small saucepan, melt the butter, then stir in the cocoa powder, oil, and water. Heat to a boil, then boil for 1 minute. In the meantime, in a small bowl, mix together the eggs buttermilk, and vanilla. Pour the heated mixture over the flour mixture and stir. Add the egg and buttermilk mixture and stir until well combined. Pour the batter into the prepared pan and bake for 35 to 45 minutes or until a tooth pick inserted into the center comes out clean. Allow to cool for at least 30 minutes before icing.

Step 4

Combine the butter and cocoa in a small saucepan. Cook until the butter is melted completely. Take off the heat and stir in the vanilla.

Step 5

Pour the powdered sugar into a large bowl and pour the hot mixture over the powdered sugar. Stir to combine. Add 1 tablespoon of buttermilk at a time until you get the icing to a pourable consistency, but not too thin. Pour over cake and spread to coat.