Deluxe New-Fashioned Chocolate Cake

1 ounce unsweetened baking chocolate 1/2 cup unsweetened cocoa powder 1/3 cup spring water2 1/4 cups unsifted cake flour1 1/4 teaspoons baking powder1 teaspoon baking soda 1/2 teaspoon salt 1/4 cup sweet butter, at almost room temperature 1/2 cup drained, unsweetened applesauce (from 3/4 cup undrained)1 2/3 cups light brown sugar, packed1 egg yolk, at room temperature3 whole eggs, at room temperature1 teaspoon vanilla extract 1/2 cup waterBreak baking chocolate into pieces; place in a small heavy-bottom saucepan with cocoa and 1/3 cup water. Over low heat, stir constantly until chocolate has melted. Remove from heat and cool.Set oven rack to center position and heat oven to 350 degrees. Lightly spray the inside of a 13-by-9-inch baking pan with vegetable oil and flour spray (Bakers Joy, for example). Set aside.Sift the flour, baking powder, baking soda and salt together three times. Set aside.In the large bowl of an electric stand mixer cream the butter for 2 minutes on medium-high speed. Add the sugar and cream together for 3 minutes. Add the drained applesauce; mix at medium-high for 1 minute. Add the vanilla and mix for 30 seconds. Add the cooled chocolate mixture and mix for 1 minute. Add the egg yolk and mix for 20 seconds. Add the whole eggs, one at a time, mixing for 15 to 20 seconds each.Stop the mixer; add all the sifted flour mixture and mix at low speed until just blended. Add remaining 1/2 cup water and mix on low speed until just incorporated, about 20 seconds. With a wide rubber spatula scrape the sides of the bowl and fold and stir the batter a few times until incorporated.Pour the batter into the prepared pan, smoothing out the surface, and bake for 35 minutes or until a toothpick inserted into the center comes out clean. Cool.Serves 15.Nutrition values per serving: 186 calories (29 percent from fat), 6 g fat(3.2 g saturated fat), 31.6 g carbohydrate, 0.6 g fiber, 3.3 g protein, 65 mg cholesterol, 180 mg sodium.LeanTip: A boiled or seven-minute vanilla frosting is virtually fat free and makes a dandy topping for this cake.