Preparation / Directions:
Heat oven to 350 degrees. Spray 12-cup bundt cake pan with non-stick cooking spray. Heat milk in 1 1/2-quart saucepan over medium-low heat until just beginning to simmer; remove; remove from heat. Stir in cocoa. Let stand 2 to 3 minutes. Stir in applesauce and vanilla. Mix flour, 1 1/4 cups of the sugar, the baking powder, baking soda and salt in large bowl. Stir in milk mixture just until blended.
Beat egg whites in medium bowl on medium speed until stiff. Gradually beat in remaining 1/4 cup sugar. Carefully fold egg whites into chocolate batter. Pour into pan.
Bake 35 to 40 minutes or until cake springs back when touched lightly in center. Meanwhile, prepare Warm Chocolate Sauce. Cool cake 10 minutes; remove from pan. Top slices of warm cake with frozen yogurt and chocolate sauce. Warm Chocolate Sauce: Mix sugar, cocoa and cornstarch in 1-quart saucepan. Stir in buttermilk. Heat to boiling over medium heat, stirring occasionally; reduce heat. Simmer about 7 minutes, stirring occasionally, until thickened; remove from heat. Stir in vanilla. Serve warm. Refrigerate any remaining sauce.