• Grease an 18x13" pan and preheat the oven to 350 degrees Fahrenheit.
• In a medium saucepan over medium heat, add water, butter, and cocoa powder. mixture is brought to a boil.
• In the meantime, combine the flour, sugar, baking soda, and salt in a another basin.
• Combine the sour cream, eggs, and vanilla in a separate small bowl.
• Stir until mixed before adding the sour cream/egg combination to the flour mixture.
• Pour the boiling chocolate mixture into the batter after taking the pan off the heat. Mix thoroughly to remove all lumps.
• Mixture should be poured onto the pan that has been prepared and spread evenly with a spatula.
• Bake for 15-20 minutes, or until set, in a preheated oven (mine is usually done around 15 minutes).
• Prepare the icing and start the cake at approximately the halfway point.

For the Chocolate Sheet Cake Frosting

• Butter, chocolate, and milk are added to a pot. mixture is brought to a boil.
• When it boils, turn off the heat and toss in the powdered sugar. To remove any lumps, I like to whip the mixture with a hand-held mixer.
• Over a hot cake, drizzle hot frosting. Spread it evenly over the cake using a spatula. Before eating, give the icing 10 minutes to set.