Preheat the oven to 375 degrees farenheit with the rack in the center position. Butter and flour a 9x13 inch pan.

Place the butter, cocoa and water in a deep saucepan. Bring to a boil, whisking to get out lumps. Remove from heat and cool 10 minutes.

Combine the flour and sugar in a large mixing bowl and set aside. Stir the baking soda into the buttermilk and add to the dry ingredients along with the eggs, vanilla and the cooled cocoa mixture. Whisk the batter until smooth and pour into the prepared pan. Bake 10 minutes, rotate the pan, and bake 5 to 10 minutes more or until the cake feels springy when touched.

Meanwhile, place the ingredients for the glaze into the same saucepan (without rinsing first). Whisk together and bring to a boil. Pour the hot glaze over the hot cake. Sprinkle with nuts, if desired, and serve the cake warm, with vanilla ice cream. Best eaten the day of baking!

9x13 inch pan
12 servings

1 cup (2 cubes) butter
1/4 cup unsweetened cocoa powder
1 cup water
2 cups flour
1 cup sugar
1 teaspoon baking soda
1/2 cup buttermilk
2 eggs
1 teaspoon vanilla extract

Glaze
1/2 cup (1 cube) butter
1/2 cup sugar
1/4 cup unsweetened cocoa powder
3/8 cup (1/4 cup plus 2 tablespoons) milk
1 teaspoon vanilla extract
1/2 cup chopped walnuts, pecans, or almonds to sprinkle on top (optional)

Vanilla ice cream for serving.