The 73rd recipe I made from The Modern Baker by Nick Malgieri, was the one for Sour Cream Brownies, on page 274. (We are not publishing recipes from the book, so if you like what you see, buy the book and bake along with or without us).
The ingredient list: butter, chocolate, dark brown sugar, eggs, sour cream, salt, vanilla, all-purpose flour, and walnuts.
I maybe should have baked these a little less to get a less firm center as these were cake-like, but then others said that cake-like brownies are great, so I'm not really sure as it's not like I eat brownies to know the difference, being full of chocolate and all as they are, of course.
Mark liked them very much, the combination of a nice moist brownie with the sour cream addition and the nuts appealed to him enough to request a repeat soon. He was happy that I made them when Matt was at school so that he actually could get more than one or two. I froze some of them for Matt when he would be home over Christmas break, and those appeared to be just as well received as the fresh ones.
Here are posts from others who made them: Abby, Marie, and Renee. If you would like to bake along or be a part of the Modern Baker group, you will find all that, plus a tab to link to the blogs posting, with the blogroll here.