Makes 2-9" round or 3-8" round pans
We found this cake to be a little on the crumbly side, especially the day of baking. When frosting make sure to do a thin "crumb coat" and then another layer of icing.
4 oz. unsweetened chocolate , chopped
1/4 c. (30g) Dutch-processed cocoa powder
1 1/4 c. (10oz) water, boiling
1-1/2 c. (188g) unbleached all-purpose flour
1 tsp. baking soda
1/4 tsp. (4g) table salt
8 oz. unsalted butter (2 sticks), softened
1 1/2 c (300g) packed dark brown sugar
3 large eggs
1/2 c. (4 oz) sour cream
1 tsp. vanilla extract
1. Adjust oven rack to upper- and lower-middle positions; preheat to 350 degrees. Grease three 8-inch cake pans (or 2 9-inch) with butter and line bottom of each pan with parchment paper round (or dust with flour). Place hocolate and cocoa in medium bowl; pour boiling water over and whisk until smooth. Sift flours, baking soda, and salt; set aside.
2. Place butter in bowl of standing mixer and beat at medium-high speed until creamy, about 1 minute. Add brown sugar and beat on high until light and fluffy, about 3 minutes. Add eggs one at a time, beating 30 seconds after each addition. Reduce speed; add sour cream and vanilla and beat until combined. Turn mixer to low and add about one third of flour mixture, followed by about one half of chocolate mixture. Repeat, ending with flour mixture; beat until just combined. Remove bowl from mixer; scrape bottom and sides of bowl with rubber spatula and mix gently to thoroughly combine.
3. Divide batter into cake pans, smooth batter to edges of pan. If baking three 8-inch cakes, place two pans on lower-middle rack and one on upper-middle rack. Bake until skewer inserted in center comes out clean, 20 to 23 minutes for 8-inch cakes, 25-30 for 9-inch pans. Cool on wire rack 15 minutes. Run knife around pan perimeter to loosen. Invert cakes onto large plate; peel off parchment, and reinvert onto lightly greased rack. Cool completely before icing.