I had the same chocolate birthday cake for 20 years. (In case you need it, the chocolate fudge cake recipe is in How Cooking Works and you really do need to use the sour cream and to make it two days ahead.) Since wheat flour is no longer an option, I have a new birthday cake recipe. It’s a pleasantly short list of ingredients, and not a complicated recipe. You do need to be precise with the baking time, temperature, and whipping the egg whites enough. It yields a lighter flourless chocolate cake with good texture and (relatively) little damage to your waistline.
Where to find it: Moosewood Restaurant Book of Desserts, Flourless Chocolate Cake