I got the idea of the sour cream addition from the cooks illustrated site it offsets the strong chocolate, some suggest adding instant coffee which I would have but forgot. when I tasted these warm I hated them room temp still was not sure but after a day in the fridge I could not stop eating them. I think the bite of the sour cream might take a minute to get used to but when you do look out. I do suggest only using the double chocolate mix because of the sour cream addition. they also say you must end with the brownie so the mixture cooks correctly to insure no dry edges & not soggy.