1. Grease and flour 13x9x2-inch baking pan. Heat oven to 350°F.
2. Stir together flour, sugar, baking powder, baking soda and salt in large bowl. Add shortening, butter, vanilla and buttermilk; beat on low speed of electric mixer until blended. Beat 2 minutes at medium speed. Add egg whites and beat 2 additional minutes. Pour batter into prepared pan.
2. Bake 30 to 35 minutes or until wooden pick inserted in center comes out clean. Cool in pan 15 minutes. Meanwhile, prepare CHOCOLATE SYRUP GLAZE. Carefully pierce cake in pan with fork to depth of cake making parallel rows about 1 inch apart, covering both length and width of cake. Spoon prepared glaze over warm cake allowing the mixture to flow into holes and completely glaze top. Refrigerate several hours or overnight.
4. Prepare CHOCOLATE SYRUP WHIPPED CREAM; frost cake. Refrigerate leftover cake. 15 to 18 servings.
CHOCOLATE SYRUP GLAZE: Sprinkle 1 envelope unflavored gelatin over 1/4 cup cold water in small bowl; let stand 2 minutes to soften. Add 1/4 cup boiling water; stir until gelatin is completely dissolved and mixture is clear. Stir in 1 cup HERSHEY'S Syrup. About 1-1/2 cups glaze.
CHOCOLATE SYRUP WHIPPED CREAM: Beat 1 cup (1/2 pt.) cold whipping cream, 1/3 cup HERSHEY'S Syrup and 2 tablespoons powdered sugar in medium bowl until stiff. Use immediately or cover and refrigerate. About 2 cups whipped cream.
* To sour milk: Use 1 tablespoon white vinegar and milk to equal 1 cup.
Note: 1 package (18.5 oz.) white cake mix baked as directed on package can be substituted for above white cake. (DO NOT USE PUDDING-IN-THE MIX CAKE.)