Creating Texas Sheet Cake is a breeze if you follow these simple steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Grease and flour a 13×18-inch baking sheet or pan.
2. Mix Dry Ingredients: In a large bowl, combine the flour, granulated sugar, cocoa powder, baking soda, and salt. Whisk together until well blended.
3. Melt Butter: In a saucepan, combine the butter and water. Bring to a boil, then remove from heat.
4. Combine Mixtures: Pour the hot butter mixture into the bowl with the dry ingredients. Stir until just combined.
5. Add Wet Ingredients: Add the buttermilk, eggs, and vanilla extract to the batter. Mix until smooth and well incorporated.
6. Pour Batter: Pour the batter into the prepared baking sheet, spreading it evenly.
7. Bake: Place the pan in the preheated oven and bake for 25-30 minutes, or until a toothpick inserted in the center comes out clean.
8. Prepare Frosting: While the cake is baking, melt the butter for the frosting in a saucepan. Stir in the cocoa powder and milk, bringing it to a gentle boil.
9. Mix Frosting: Remove from heat, and whisk in the powdered sugar and vanilla extract until smooth. If desired, fold in the chopped nuts.
10. Frost Cake: Once the cake is out of the oven and slightly cooled, pour the warm frosting over the top, spreading it evenly.

These steps will lead you to a delicious Texas Sheet Cake that is sure to impress your family and friends!