Get supplies and ingredients and wash hands. Preheat oven to 350 degrees and either spray or grease the 10 X 13 pan.
Mix wet ingredients (cocoa,butter,and water).
Mix wet and dry ingredients for 2 minutes.
Mix until you get a batter consistency.
Break eggs into another bowl and beat eggs. Add beaten eggs to batter.
Add buttermilk, baking soda, and vanilla extract to batter mixture.
Mix for 2 minutes.
Pour batter into a pan.
Spread out evenly.
Put batter in the oven.
Set timer for 20 minutes.
When toothpick comes out clean there done. While cooling make frosting.
Mix butter,milk,sugar and boil for 2 minutes.
Beat until frosting consistency.
Spread frosting out on brownies.
Let frosting set and cut.