1. Heat oven to 350°F. Line bottom of 15-1/2x10-1/2x1-inch jelly-roll pan with parchment paper or line with foil (extending slightly over sides); grease foil.
2. Stir together 1/3 cup cocoa and water in small bowl until mixture is smooth. Stir in butter and vanilla; cool.
3. Combine egg yolks and 1/2 cup sugar in large bowl; beat on medium speed of mixer until light and fluffy, about 5 minutes. Add chocolate mixture and almonds, beating until well blended.
4. Beat egg whites in another large bowl until foamy. Gradually add remaining sugar, beating until stiff peaks form. Fold 1/4 of egg white mixture into chocolate mixture. Add remaining whites, folding well. Pour batter into prepared pan.
5. Bake 18 to 20 minutes or until cake springs back when touched lightly in center. Dust cake with 1 tablespoon cocoa; cover with clean, dry towel. Cool completely in pan on wire rack.
6. Cut cake into 4 equal pieces. Remove paper or foil before placing on serving plate. Prepare COCOA WHIPPED CREAM; reserve 1-1/4 to 1-1/2 cups to frost sides and ends of cake. Place one cake layer on plate; spread with COCOA WHIPPED CREAM.
7. Repeat layering, ending with whipped cream. Spread reserved whipped cream on all sides of assembled cake. Garnish as desired. Refrigerate until serving time. Cover; refrigerate leftover dessert. About 18 servings.
COCOA WHIPPED CREAM: Combine 1-1/2 cups cold whipping cream, 1/3 cup sugar, 3 tablespoons HERSHEY'S Cocoa and 3/4 teaspoon vanilla extract in large cold bowl; beat with cold beaters until stiff. About 3 cups whipped cream.
* To toast almonds: Heat oven to 350°F. Spread 1/3 cup blanched slivered almonds in thin layer in shallow baking pan. Bake 8 to 10 minutes, stirring occasionally, until light golden brown. Cool completely. To grind, use food processor.