Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 15x10x1 inch baking pan.
In a medium bowl, mix together the flour, sugar, baking soda, and salt. Set aside.
In a large saucepan, melt the butter, water, and cocoa powder together over low heat. Once melted, remove from heat and stir in the beaten eggs, buttermilk, and 1 teaspoon of vanilla extract.
Pour the wet ingredients into the dry ingredients and mix until well combined.
Pour the batter into the prepared pan and bake for 20 to 25 minutes, or until a toothpick inserted into the center of the cake comes out clean.
To make the icing: In a medium saucepan, combine the butter, cocoa powder, and milk. Cook over low heat until the butter is melted, stirring occasionally. Remove from heat and stir in the vanilla extract and confectioners' sugar until smooth. Spread over the warm cake.
Interesting Facts
This Texas Sheet Cake II is a classic Southern recipe.