• Preheat the oven to 350 degrees Fahrenheit and grease a 18x13 inch pan.
• Add water butter cocoa powder to a medium saucepan over medium heat. Bring mixture to a boil.
• Meanwhile, in a separate bowl mix together the flour, sugar, baking soda and salt.
• In another small bowl mix together the buttermilk, eggs and vanilla.
• Add egg mixture to the flour mixture and mix with a spatula until combined.
• Once the chocolate mixture in the saucepan is boiling, remove it from heat and pour it into the batter. Mix with a whisk until combined and no lumps remain.
• Pour mixture into the prepared pan and smooth with a spatula to make sure it is dispersed in an even layer.
• Bake in a preheated oven at 350 degrees Fahrenheit for 15-20 minutes or until set.
• When the cake is about half-way through cooking, prepare the frosting.

Frosting

• Add milk, cocoa and butter to a saucepan. Bring mixture to a boil.
• Once boiling, remove it from the heat and stir in powdered sugar and vanilla using a whisk.
• Pour hot icing over hot cake. Use a spatula to spread it evenly over the cake. Allow frosting to set for about 10 minutes before eating.