Mix all ingredients together in 13x9 inch pan with a spoon. (I always mix it in a bowl and then pour it into the pan, because it is not so messy.)
After it is mixed well (you don't need to beat it), put it in 350 degree oven for about 30 minutes.
Ice with small amount of chocolate frosting, if desired. It is pretty rich already.
If I'm not going to serve it from the pan, I grease and flour the pan before pouring the batter in.