Chocolate Sheet Cake (yes, this is THE cake)

Cake

2 1/3 cups flour
2 cups sugar
1 tsp baking soda
1 cup butter
1 1/4 cup water
4 Tbsp cocoa
1/2 cup buttermilk
2 eggs, beaten
1 tsp vanilla extract

Mix flour, sugar, and soda in bowl. Bring butter, water, and cocoa to a boil in a saucepan. Pour over dry ingredients. Mix thoroughly. Add buttermilk, eggs, and vanilla. Beat well. Pour into a greased 9 x 13 pan and bake at 350 for 30 minutes.

Frosting
1/2 cup butter
4 Tbsp coca
6 Tbsp buttermilk
1 tsp vanilla
1 lb. powdered sugar

Heat butter, cocoa, and buttermilk to a boil. Remove from heat and mix in vanilla and sugar.

[Lauren's edit: Now go on a 10-mile run! Twice.]