Texas Sheet Cake

This recipe is so fast and easy you can make it while your guests are at the table and bake and frost it before dessert and serve it warm with vanilla ice cream. While at Danielle and Jordan's we couldn't find it in the blog, so it must be here!
Mix in saucepan:
2 squares butter
3 TB baking cocoa
1 cup water
If you have buttermilk, great, if you don't add 1 TB vinegar to 1/2 c milk and set aside at this point.
Bring to a boil the cocoa mixture for about a minute. Pour it over 2 cups flour and 2 cups sugar in a mixing bowl. Mix till smooth. Add 1/2 cup soured milk or buttermilk, 1 tsp. cinnamon, 2 eggs, 1 tsp. vanilla and 1 tsp. baking soda. Bake in a jelly roll pan for 18-20 min.at 375 degrees. Check to make sure it comes clean in center with a knife. While it is cooking melt in saucepan 1 square butter, 4 TB cocoa and 6 TB milk. Just bring to a boil then remove from heat and add 1 tsp. vanilla and 1 pound powdered sugar, and 1 cup chopped walnuts or pecans. Beat well until smooth and spread on cake right out of the oven.