Step 1 Preheat the oven to 375 degrees Fahrenheit. Bring oil, water and cocoa to a boil. Remove from heat.
Step 2 Add the dry ingredients to the oil/water/cocoa mixture. Stir to combine.
Step 3 Beat two eggs in a bowl. Add the buttermilk (or sour cream) and baking soda. Mix well.
Step 4 Add egg mixture to the chocolate mixture and mix well. Pour batter into a greased jelly roll pan (16x10x1). Bake in a preheated oven for 20 to 22 minutes. Meanwhile, make the frosting.
Step 5 Bring butter, cocoa, and milk to a boil in a saucepan.
Step 6 Remove from the heat and add the powdered sugar (sift it first if lumpy). Add the vanilla. Spread the icing on the Texas Sheet Cake while it is still warm. Sprinkle with chopped nuts, if desired. ENJOY!