Preheat oven to 400˚ F. Grease a 13x9 baking pan.

In a saucepan, combine the butter, water, cocoa, and vegetable oil. Bring to a boil over medium heat, stirring constantly. Once boiling, remove from heat.

In a heat-safe bowl, combine the flour, sugar and salt. Pour the hot cocoa mix over the dry ingredients. Mix well. Stir in the buttermilk, eggs, baking soda, and vanilla extract.

Pour the brownie batter into a 13x9 baking pan. Bake for 20-25 minutes or until a toothpick entered into the center comes out clean.

Make the frosting by combining the butter, cocoa, and buttermilk in a saucepan. Bring to a boil. Add the sifted powdered sugar and vanilla. Pour over the warm brownies. Let cool and serve.