Oklahoma Cake

Why I Love This Recipe
I'm not really sure where this cake got its name - maybe the author, LaVerne, was from OK. It is an interesting recipe for a few reasons: it is baked in a jelly roll pan, the flour ad sugar are sifted together, and the icing goes on while it and the cake are still hot.
Ingredients You'll Need
Cake
2 cups sugar
2 cups flour
1/2 cup shortening
1/2 cup butter (1 stick)
1 cup water
4 Tbsp cocoa
1/2 cup buttermilk (or use 1 tbsp. vinegar plus milk to make 1/2 cup)
2 eggs, beaten
1 tsp baking soda
1 tsp vanilla
Icing
1/2 cup butter (1 stick)
4 Tbsp cocoa
1/3 cup milk
1 pound of powdered sugar (approximately 3 1/2 to 4 cups)
1 cup chopped nuts (walnuts or pecans work)
Directions
Preheat the oven to 400 degrees.
Sift together the flour and sugar into a large bowl.
In a saucepan, combine the butter, shortening, water, and cocoa. Bring to a boil and remove from heat.
While it is still hot, pour the mixture in the saucepan over the flour and sugar.
Add the buttermilk, eggs, soda, and vanilla. Stir until well combined.
Pour into an ungreased 16 X 11 X 2 inch pan (jelly roll pan).
Bake for 25 minutes.
While cake is baking, make the icing. Bring the stick of butter, cocoa, and milk to a boil in a saucepan.
Add 1 pound of powdered sugar, vanilla, and nuts, and stir to combine.
Spread over the cake while both are still hot. Leave cake in pan to cool.