No need to make a trip to the Lone Star State to learn how to make the best Texas Sheet Cake from scratch. This rich chocolate cake is topped with a buttery cocoa frosting that has a delicious crackly texture.
Preheat oven to 400 degrees. Line a 10-inch by 15-inch jelly roll pan with parchment paper or nonstick spray. In a small saucepan, whisk together butter, water, and cocoa. Bring to boil; remove from heat.
Meanwhile, in large bowl whisk together flour and sugar. Stir in boiled mixture. Beat in eggs, baking soda, vanilla, and sour cream. Pour into prepared pan and bake 20 minutes. Cool completely.
While cake is cooling, in medium saucepan whisk together butter, milk and cocoa and bring to a boil. Remove from heat and stir in powdered sugar and vanilla until smooth. Spread on cooled cake while frosting is hot. Cool and cut into 24 bars.