1. Heat oven to 350°F. Grease and flour 13x9x2-inch baking pan.
2. Stir together flour, 1 cup sugar, cocoa, baking soda and salt in large bowl. Add buttermilk, oil and egg yolks; beat on medium speed of mixer until smooth. Using clean beaters, beat egg whites in small bowl until soft peaks form; gradually add remaining 1/2 cup sugar, beating until stiff peaks form. Gently fold egg whites into chocolate batter. Pour batter into prepared pan.
3. Bake 30 to 35 minutes or until top springs back when touched lightly. Cool in pan on wire rack. Just before serving, prepare BERRY CREAM; frost top of cake. Cut into squares; garnish with strawberries. Cover; refrigerate leftover dessert. 10 to 12 servings.
*To sour milk: Use 1 tablespoon white vinegar plus milk to equal 1 cup.
1. Place 1 cup sweetened sliced strawberries in blender conatainer or food processor bowl; puree and measure 1/2 cup.
2. Beat 1 cup (1/2 pt.) cold whipping cream in small bowl until stiff; gently fold in strawberry puree, 1 teaspoon vanilla extract and, if desired, 2 to 3 drops red food color.