from the back of the Hershey's cocoa box. It's never fail.
I frost with a simple butter cream frosting.
True story: some years back, when we were celebrating my mother's 80th birthday, my sister asked me to make a couple of my chocolate cakes. Had you been there, you'd have had the choice of chocolate cake with chocolate frosting, chocolate cake with white frosting, or the mock napolean pastry she made.
Some background. I long ago figured out that cakes made from commercial mixes had a distinctly chemical taste and stopped using them. One year, when I'd volunteered to bake for one of the class parties for my son's class, I was VERY distressed to be instructed to make cupcakes using a strawberry (if I remember correctly) mix. Sigh. I'd wanted to make one of my chocolate recipes from scratch, but because of the flavor requirement, I bought a mix.
More background. My sister (where our mom's 80th was held, and I want to say many nice things about my sister because she deserves them) occasionally would tell her kids to invite the neighbor kids to a party. She'd bake a cake, organize games, and so on. What she wanted was to establish that not all parties were the birthday parties they were used to that required presents and a gift bag going home. My sister was (and still is) wonderful. She'd always bake a cake for these parties. She always used a cake mix.
Fast forward now to Mom's 80th. As I said before, had you been there, you'd have had the choice of chocolate cake with chocolate frosting, chocolate cake with white frosting, or the mock napolean thing. To my sister's astonishment, every single person who took a piece of cake ate the entire piece. She was used to people (even kids with their notorious sweet tooths) eating only some of the cake and casting the rest aside. Not this time. Real cake made from flour, sugar, eggs, shortening, and vanilla (real vanilla, not the artificial crap) is delicious. And worth eating.
Several years ago I had a job where on Fridays I'd bake something and bring it in to share with my coworkers. It was strange and almost embarrassing to what extent they LOVED my baked goods. And how obvious it was that most of them had never had a cookie or a cake not made from a mix.
Oh, and I long ago (as in more than 30 years ago) gave up on making layer cakes. All of my cakes are sheet cakes. No fail, trust me.