I have looked in the recipes and found the durable cake recipe but I need a chocolate cake recipe that is firm for carving and I am out of sour cream right now!!
I add melted chocolate to cake recipes to make it more firm. If you don't have sour cream or yogurt, do you have chocolate pudding or coffee creamer?
If you have chocolate cake mix, try using milk in place of water--evaporated milk would be even better (amt per box instructions). Then just add 6 oz melted and cooled chocolate after it has been well blended.
Here are few recipes for you, if you want to have a look.