This is an old family favorite. Straight from my mom's cookbook. Above, it is decorated for my brother-in-law's birthday, which falls dangerously close to Halloween.
2 c. sugar
2 c. flour
1/2 tsp. salt
2 sticks butter
1 c. water
4 tbsp. cocoa
1/2 c. sour cream (light sour cream is just fine, and it also works to combine 1 tbsp. white vinegar and skim milk)
1 tsp. soda
1 tsp. vanilla
1 tsp. cinnamon
1. Sift the 2 c. white sugar, 2 c. flour, and 1/2 tsp. salt into your KitchenAid mixing bowl (sifting doesn't appear to be necessary, from my experience).
2. Put 2 sticks of butter, 1 c. water, and 4 tbsp. cocoa in a non-stick skillet on medium. Bring to a boil VERY carefully. Do not move from this pan. Stir frequently, turning over the sticks of butter, and once they are soft enough breaking them up, so that they will melt through. Also run you wooden spoon around the edges quite frequently to prevent the cocoa from hiding there and burning. As SOON as it starts to bubble, remove from heat, continuing to stir until you pour the mixture out of the hot skillet. Usually, you will know if you've burnt the mixture-the cocoa will be clumpy, and it will smell. However, I always take a taste to make sure the mixture has not been burnt, because if it is, it will ruin the whole cake.
ALTERNATE METHOD FROM PIONEER WOMAN (might help prevent unfortunate burning incidents, although I have never tried this):
Melt the 2 sticks of butter in the saucepan on medium. While it melts, boil 1 cup water. Once the butter is melted, add the 4 tbsp. of cocoa (all with the heat still on) and stir to combine. Then add the boiling water. Let bubble 30 seconds. Remove from heat.
Her recipe with photos is here. However, be warned that you should still follow the ingredients in my recipe, because she omits the essential cinnamon. Also, she almost doubles the amount of butter you want in the frosting.
3. As soon as the cocoa, water, butter mixture bubbles and melts, pour it into the KitchenAid bowl with the flour, sugar and salt. Mix well with the KitchenAid.
4. Add 2 eggs, 1/2 c. sour cream, 1 tsp. soda, 1 tsp vanilla, and 1 tsp. cinnamon. Mix again until everything is combined, using a spatula to scrape the sides and bottom of the bowl to incorporate all ingredients.
5. Pour into a greased cookie sheet pan (Pam is fine). Commercial baking sheets are the best.
6. Bake at 350 degrees for 20 to 25 minutes, until a toothpick comes out clean.
1 stick butter
4 tbsp. cocoa
6 tbsp. milk
1 lb. bag powdered sugar (I do this by eye until the consistency is right-- it is less than one bag)
1 tsp. vanilla
1. Dump (or sift, if you've got oodles of free time) half of the bag of powdered sugar into your KitchenAid bowl. Add the 1 tsp vanilla.
2. Using the method described in step 2 of the cake preparation (except for with only 1 stick of butter, and 6 tbsp. of milk rather than 1 c. of water). All of the necessary DON'T BURN THE CHOCOLATE warnings still apply.
Again, you can use Pioneer Woman's method, although I haven't tested it. For the frosting, her method is to:
Melt the stick of butter in the saucepan on medium. Once the butter is melted, add the 4 tbsp. of cocoa (all with the heat still on) and stir to combine. Allow mixture to start bubbling. Once it starts, allow to bubble 30 seconds ONLY. Turn off the heat. Then add the 6 tbsp. milk.
3. Pour the chocolate mix from frosting step # 2 over the ingredients in your KitchenAid bowl. Mix using the wire beater attachment. Use spatula to scrape down sides and bottom. No need to beat the frosting -- we are just trying to combine ingredients here.
4. Add more powdered sugar as needed, until the mixture is nicely pourable but not runny. Notice my version of the frosting is a bit more pourable than Pioneer Woman's because of the reduced butter.
5. Pour all over the cake while the cake is still warm and still in the pan (I usually let the cake rest only 5-10 minutes before getting the frosting on top).
Pouring the frosting over the warm cake allows the frosting to seep into the cake, and results in moist perfection!