No need to make a trip to the Lone Star State to learn how to make the best Texas Sheet Cake from scratch—this one is big, bold, and beautiful. If you haven’t made one before, get ready to flip over how easy it is to whip up, and how fast it’ll disappear.
Preheat oven to 400 degrees. Coat a 10-inch by 14-inch jelly roll pan with nonstick spray.
In a medium saucepan, combine butter, water, and cocoa. Bring to boil.
Meanwhile, in large bowl whisk together sugar and flour. Stir in boiled mixture. Add eggs, baking soda, vanilla, and sour cream.
Pour into prepared pan and bake 20 minutes. Cool completely.
While cake is cooling, in small saucepan bring butter, milk and cocoa to boil. Stir in powdered sugar and vanilla and beat with an electric mixer or by hand until smooth. Spread on cooled cake while frosting is hot. Cool and cut into 24 bars.