from Whole Grain Baking
makes 2 9-inch layers, 3 8-inch layers, or 2 dozen cupcakes
3/4 cup unsalted butter
1 cup packed light brown sugar
3/4 cup granulated sugar
1/2 teaspoon salt
1 1/2 cups whole wheat pastry flour
1 cup all-purpose flour
1 cup unsweetened cocoa powder
1 1/2 teaspoons baking soda
4 large eggs
2 teaspoons vanilla extract
1 cup plain low-fat yogurt
3/4 cup water
Preheat the oven to 350ºF. Grease and flour the pan or pans of your choice or line with parchment.
Cream together the butter, sugars, and salt in a large mixing bowl until fluffy, about 5 minutes. Stop to scrape the sides at least once during that time. In a separate bowl, combine the flours, cocoa, and baking soda. If lumps remain, sift or strain the flour mixture.
Add the eggs to the butter mixture one at a time, beating well (at least a full minute) after each addition, and stopping to scrape the sides and bottom of the bowl before adding the next egg. Mix in the vanilla. Add half the flour mixture and mix until evenly combined. Add the yogurt and water, and mix again. Add the remaining flour, mix, and stop to scrape the sides and bottom of the bowl once more, to make sure the batter is evenly moistened. Pour the batter into prepared pans.
Bake the cakes for the amount of time appropriate for the pan size. (30 to 35 minutes for layers, 35 to 40 for sheet cake, 25 minutes for cupcakes.) The cake is done when it pulls away from the sides of the pan and a cake tester inserted near the center comes out clean. Remove from the oven and cool for at least 15 minutes before removing from the pan. Place on a rack to cool completely before frosting.