2 1/4 cups cake flour (not self-rising)
3/4 cup unsweetened cocoa powder
1/2 teaspoon salt
1/4 teaspoon baking soda
1 cup sour cream (8 1/2 ounces)
2 1/4 sticks (1 cup plus 2 tablespoons) butter, softened
1 1/2 cups granulated sugar
1 1/2 cups packed dark brown sugar
1 teaspoon vanilla extract
6 large eggs
3 ounces fine-quality bittersweet chocolate (not unsweetened)
2 tablespoons unsalted butter

Do not preheat oven. Butter and flour a 12-cup Bundt pan. Into a small bowl sift together flour, unsweetened cocoa powder, and salt. In another small bowl stir together baking soda and sour cream. In a large bowl with an electric mixer beat together butter and sugars until very light and fluffy. Beat in extracts and add eggs 1 at a time, beating well after each addition. With mixer at low speed, add flour mixture and sour cream mixture alternately in batches, beating until just combined. Pour batter into Bundt pan and put in middle of cold oven. Set oven to 350 degrees and bake cake 1 hour and 25 minutes, or until a toothpick comes out clean. Cool cake in pan on a rack 15 minutes and turn out onto rack to cool completely.