The original version of this cake was a Sour Cream Chocolate Cake from San Francisco à la Carte, a cookbook I purloined from my Mom’s kitchen shelf as soon as I moved out on my own.
Sour Cream Chocolate Cake is a flawless, foolproof recipe…unless you happen to live in France. There is no sour cream in France. Nor is there unsweetened baking chocolate, which the recipe also calls for. I spent many years trying to adapt it to the chocolate and dairy products I could find in France, but the results just didn’t cut it. Bittersweet chocolate made the cake too sweet and too dry. Crème fraiche made it too delicate and crumbly. And so on. I gave up on making it for many, many years, till I recently came across a 90% chocolate bar in the candy section of the supermarket. 10 % chocolate was practically unsweetened….I decided to give it a go, and in the process, I altered the original quite a bit. Sour cream became yogurt. The water added became boiling water so it would melt the chocolate and butter. I ditched the electric mixer all together, omitted the baking powder (there was only a tiny amount anyhow), tweaked the amounts so they would call for a single 100 g. (3.5 oz.) bar of 90% chocolate (which is better quality than most baking chocolates and can be found in the candy section of US grocery stores), then used cocoa powder to pump up the chocolate flavor of the cake and reduce the sweetness of the icing.
This cake keeps well for several days, though the yogurt in the icing means you’re better off refrigerating it. (I don’t always do so, but then the weather in Cancale is cool.) To turn it into a birthday cake, just double the recipe and make 2 9-inch cakes.
¾ cup (120 g.) flour
¼ cup + ¼ cup unsweetened cocoa powder (30 g. plus 30 g.)
1 tsp. baking soda
½ tsp. salt
100 g./3.5 oz. (1 bar) 90% cocoa chocolate (such as Lindt Excellence), or 4 oz. unsweetened baking chocolate, broken into pieces
2 Tbs. + 2 Tbs. butter (30 g. + 30 g.) cut into small pieces
½ cup boiling water (you could also use coffee or stout beer, for extra flavor)
1 cup (200 g.) sugar
1 tsp. vanilla extract
1 egg or 1 egg substitute – 1 Tbs. flaxseed meal + 3 Tbs. water or ¼ cup aqua faba
½ cup (125 g.) + ¼ cup (62-ish g) whole plain yogurt or sour cream
¾ cup confectioners’ sugar
PREHEAT the oven to 350˚F, and coat an 8 (20 cm) or 9-inch (22.5 cm) cake pan with cooking spray.
SIFT together the flour, ¼ cup of the cocoa, the baking soda, and the salt in a large bowl. Set aside.
PLACE 80 g. (8 squares) of the 90% chocolate or 3 oz. unsweetened baking chocolate in a medium bowl with 2 Tbs. of the butter, and pour the boiling water over top. Let stand until the butter and chocolate are melted.
WHISK in the sugar, vanilla extract and egg. Alternate adding the flour-cocoa mixture and ½ cup yogurt or sour cream, then whisk the batter 30 seconds or until smooth and creamy.
SPREAD the batter in the prepared cake pan, and bake 25 to 30 minutes, or until a toothpick inserted in the center comes out clean. Cool 10 minutes, then unmold onto a wire rack to cool completely.
MEANWHILE, to make the icing: Melt the remaining 20 g. (2 squares) 90% chocolate or 1 oz. unsweetened baking chocolate and 2 Tbs. butter in a double-boiler or a microwave set on 50% power. Whisk in the remaining ¼ cup cocoa powder, then 2 Tbs. of the remaining ¼ cup yogurt. Alternate adding the confectioners’ sugar and remaining yogurt, and whisk until smooth. Cool the icing to allow it to thicken, then spread on the cake.
NOTE: I’ve tested this with gluten-free flour and it works best if you add an extra egg (2 eggs total) to the batter. The extra egg gives the cake a little more structure.