Texas Sheet Cake

This dessert is a great choice to throw together quickly and will feed a large group.  I was given this recipe by a friend of mine named Marlyce.  It's very different from any other cake I have ever made as this is made on the stove top and baked for a very short amount of time.  The frosting is poured on as soon as it is removed from the oven.
I have received great feedback from this recipe, and many suggestions.  My sister thinks it tastes like a molten lava cake.  My mother says"warm fudge",  she also would like to try it refrigerated.   I think I would like to try chopped macadamia nuts sprinkled on top in lieu of the walnuts, or leave the frosting off completely and sprinkle with powdered sugar.
 Please let me know what your variations are.

Texas Sheet Cake

3 sticks of butter
1 cup of water
8 tbsp of cocoa powder (divided)
2 cups of sugar
1/2 tsp salt
1 tsp baking soda
2 cups flour
2 eggs
1/2 cup sour cream
1 cup chopped walnuts
1 box confectioners sugar
2 tsp vanilla
6 tbsp milk

1) In a large sauce pan bring to a slow boil 2 sticks of butter, 1 cup of water, and 4 Tbsp of cocoa powder. Remove from heat at this time.

2) Add all at once 2 cups of granulated sugar, 1/2 tsp salt, 1 tsp baking soda, 2 cups of flour. Use whisk  to combine well.
3) At this point add 1/2 cup of sour cream, mix well, then add 2 eggs.

4) Spread mixture into a cookie sheet ( 15x10x1 inch) that has been sprayed with cooking spray

5) Bake in a 350 Degree oven for exactly 20 minutes
6) While cake is baking wash sauce pan, and melt together  1 stick of butter, 6 Tbsp milk, and 4 Tbsp cocoa
7) As soon as mixture boils add 1 box of confectioners sugar and 2 tsp of vanilla extract.  When sugar is incorporated well add chopped nuts.

8) When you remove the cake from the oven, pour the hot frosting mixture over the cake.  Use a large off-set spatula to spread evenly.

9) When cool, slice into squares and serve.