Preheat oven to 350 degrees. Lightly grease and flour a 9x13 cake pan.

Cream together sugar, vegetable shortening and eggs, using an electric hand mixer or stand mixer. Beat well for 2-3 minutes.

In a separate large bowl, sift together flour, cocoa, baking soda and salt. Add dry, sifted ingredients to the wet ingredients, along with 1 cup of buttermilk, and mix well on LOW speed.

Once blended, slowly pour in 3/4 cup of boiling water, and a teaspoon of vanilla extract. Blend on low until batter is fully mixed together. Pour batter into a greased and floured 9x13 baking pan, and distribute batter evenly.

Bake at 350 degrees for 35 minutes, or until toothpick inserted into middle of cake comes out clean.

While cake is baking, make frosting. Melt butter in saucepan on low heat. Add cocoa powder and mix well with a spoon. Add salt, vanilla, and milk; mix well. Add powdered sugar. Mix until frosting is not too thick, but "pourable". Add additional milk to thin... add additional powdered sugar to thicken, as needed.

When cake is done, remove from oven. Let rest for 2-3 minutes, then poke holes over surface of cake every couple inches (I use a chopstick!). Pour frosting over surface of cake, and spread to cover. Let cake cool to room temperature, then slice and serve!