Preheat oven to 375°F. Butter a 16x10x1 inch baking pan (or Baker’s half sheet pan.)
Mix flour and sugar in a large mixing bowl; set aside.
In a saucepan, combine butter, cocoa, and water; bring to a boil and take off heat.
Stir the butter/cocoa mixture into the flour/sugar mixture. Add sour cream, eggs, vanilla, baking soda and salt. Mix well.
Pour into prepared pan. Bake 15-20 minutes or until cake tests done.
In a saucepan, combine butter, cocoa, and milk. Bring to a boil and remove from heat.
In a mixing bowl, combine powdered sugar and vanilla.
Add hot butter/cocoa mixture to sugar mixture; beat well.
Spread icing over cake as soon as it comes out of the oven.
Enter your zip code to find Challenge products near you.
Subscribe and get recipes, techniques, and special offers delivered monthly to your inbox.