Texas Sheet Cake

Bring to boil in medium saucepan over medium heat:
1 cup butter
1 cup water
1/2 cup cocoa

Take off heat and add:

2 cups sugar
2 eggs
1 tsp. soda
1 tsp. cinnamon
1/2 cup buttermilk
1 tsp. vanilla
Mix well with a hand mixer and then add
2 cups flour
Mix with mixer and pour into cookie sheet. (10x15 inches)

Bake for 20-25 minutes at 400 degrees.
Allow cake to cool and then frost with frosting.
Frosting:

Combine in a medium sauce pan and bring to a boil over medium heat:

1 cup butter
1/2 cup milk
1/2 cup cocoa

Remove from heat and add:
5 cups powdered sugar
2 tsp. vanilla
Beat with mixer until smooth
Cool before frosting the cake

I got this recipe when I was very young, maybe 6th grade? It is a Moutain Fuel recipe, anyone remember them?  My Mom took me to a cooking demo, that may very well have been the beginning? This is a great standard recipe. I have added the cinnamon and I doubled the frosting as it never seemed quite enough to cover a sheet cake.
The thing that makes this cake is the frosting is very fudgy and there is lots of it.

*This can be made as a 9x13 cake. Cook 25-30 minutes and cut frosting recipe in half.