I must agree with the overwhelming consensus both that chocolate cake must have the actual cake be chocolate, and that yellow cake with chocolate frosting is the best, especially that kind with pudding in the mix. Look at German-chocolate cake. It doesn’t even have chocolate frosting, yet it’s called chocolate cake.
Wow, trippy. I’ve typed the word chocolate so much, it doesn’t look like a real word anymore. Chocolate, chocolate, chocolate…man, that’s weirding me out.
Sauron, so what would you call chocolate cake mix with a white icing?
What do I call yellow cake mix with chocolate frosting? I call it a waste of chocolate frosting, that’s what I call it. Yellow cake is vile and wrong, an abomination unto heaven, world without end, amen.
In public, though, I tend to refer to it as “yellow cake with chocolate frosting” and I try not to look like someone just handed me a rancid squid.
Chocolate cake is cake made with chocolate batter, with or without chocolate frosting. (I’m partial to marshmallow or cream cheese frosting with it, myself. Or the ultimate tummy-ache on a plate cake, the Mississippi Mud cake. )
Must start south of here somewhere - that’s yellow cake with chocolate frosting to me.
Yuk. Cream cheese belongs on a bagel.
A photographic negative.
Devil’s food cake is a specific kind of chocolate cake, which is made of dark chocolate and is unusually rich. Devil’s food cake does always have a chocolate fudge icing on it, but you can’t put chocolate icing on any old chocolate cake and have it be called devil’s food unless you’re crazy, which obviously quite a few people in this thread are. 
Yellow cake with chocolate frosting is a chocolate-frosted cake. The word “cake” defaults to yellow cake in my experience, and so “chocolate-frosted” modifies it; “chocolate cake” is a cake made with chocolate batter, no matter what sort of frosting it has on it.
My Momma used to call yellow cake with chocolate frosting “chocolate cake.”
Are you calling my Momma a liar?
Not a liar. Just crazy.
Are you sure she’s your Momma?
Yellow cake with chocolate frosting never had a name where I grew up. The “chocolate” in chocolate cake always refers to the cake, not the icing.
If I ask someone “What kind of cake is that?” I want to know what’s underneath the frosting. If they said “Chocolate Cake” and cut me a slice and the cake wasn’t chocolate, only the icing, I’d smack 'em.
On related chocolate cake issues, German chocolate cake is specific kind of chocolate cake, which never has chocolate frosting. And as others have pointed out, Devil’s Food cake is a specific type of chocolate cake with chocolate frosting.
I can sove your problem. Take your box of yellow cake mix, dump in a pack of chocolate pudding mix and a cup of ginger ale. Violá! Chocolate cake batter!
No enriched Nigerian uranium jokes yet?
Geez, what’s wrong with you people?
My head bowed in abject depression, I humbly direct your attention to post #19 in this thread.
Dammit! I mean #20.
If “chocolate cake” has to have actual chocolate color and flavor in the cake itself, then I demand that “coffee cake” be coffee flavored!
Because he’s more of a pie or cobbler man, don’t you know?
OP: Chocolate cake. But it’s different from chocolate cake. It’s all in what who made it calls it.
Yellow cake + chocolate icing?
Well, that would be butter cake with chocolate icing, Bob.
Chocolate cake + white icing?
Well, that would be chocolate cake with vanilla icing.
**
However**
Orange cake + chocolate icing?
That would be jaffa cake.
As the Internet’s most vocal chocoholic, “chocolate cake” requires that the actual cake be chocolate. Any kind of icing/frosting, or no icing/frosting at all, is allowed, as the type and presence of frosting in no way influences what type of cake it is.
Yellow cake with chocolate frosting, while yummy, is not chocolate cake. It is yellow cake. Yellow cake without chocolate frosting is yummy, too, but the chocolate frosting makes it better.
The best cake is chocolate cake with whipped cream frosting and strawberry filling. This is the cake I request every year for my birthday. I never ever get it. Because my birthday is also my sister’s birthday, and she does not like chocolate. This makes me sad. 
White cake is an abomination.
Lemon cake is acceptable, if neither chocolate cake nor yellow cake is available. Lemon cake is yellow, but it is not yellow cake. It is lemon cake.
Angel food cake is passable, but only with either chocolate frosting or strawberries and whipped cream on it.
Milk chocolate frosting. Angel food cake with milk chocolate frosting. It’s a birthday tradition for me each year, and the only cake worthy of such an honor.