How can I get my chocolate cake to taste less like a brownie?

I've been testing out cake recipes, and I'm having a bit of difficulty creating a chocolate cake that doesn't taste like a brownie.

What I want is a light, moist chocolate cake (doesn't everyone?), but the cake currently has the same texture and taste as a cakey brownie. I've tried aerating it more by beating the egg whites before I add them and adding more rising agent (tried baking powder, baking soda, and a combination of the two), but that resulted in the cake rising too much and overflowing the tin.

I've also tried adding yogurt to make it more moist, but that only made it denser.

I'm using real chocolate in my cake because I want it to taste super dark chocolatey. I've read a lot of cake recipes and I don't see very many that use block chocolate, usually only cocoa powder. Is this the cause of my problem?