OMG you have soooo many recipes to choose from! I myself have made the Epicurious Double Chocolate Layer cake, Hershey's perfectly chocolate cake, and One Delicious Cake. None of them even held a candle to the tweaked version of the Scott Clark Woolley Fudge Brownie cake IMHO. I have never found a better chocolate cake, not made by myself, and not made at a bakery, since discovering that recipe. It is incredibly moist, dense but still cakey (i.e. not dense like a brownie as the name suggests), rich and chocolatey.
Here's the link, it's on p3 of another thread. http://forum.cakecentral.com/cake-decorating-ftopic-52587-30.html
I finally had someone post back with their results (different thread than the above one) and they were thrilled; her husband said it was the best CAKE he'd ever eaten. I had the same feedback the very first time I baked it.
Note, the egullet mod who posted the recipe is the one who stated (in the recipe notes) that the top domes and cracks. I personally don't have that problem with this cake.