1. Heat oven to 350°F. Grease and flour 12-cup fluted tube pan.
2. Stir together chocolate bar pieces, butter and water in medium bowl until chocolate is melted. Stir together flour, sugar, cocoa, baking soda and salt in large bowl; gradually add butter mixture, beating until well blended. Add eggs, sour cream and vanilla; beat on medium speed 1 minute. Pour batter into prepared pan.
3. Bake 50 to 55 minutes or until wooden pick inserted in center of cake comes out clean. Cool 10 minutes; remove from pan to wire rack. Cool completely. Meanwhile, prepare CHOCOLATE COATED ICE CREAM CONE. Drizzle ORANGE FROSTING over cake. Place ice cream cone into center of cake for pumpkin stem. Using leaf decorating tip, pipe leaves onto 'pumpkin' with DECORATOR FROSTING. 10 to 12 servings.
CHOCOLATE COATED ICE CREAM CONE: Place 1 cup HERSHEY'S SPECIAL DARK Chocolate Chips or HERSHEY'S Semi-Sweet Chocolate Chips and 1 tablespoon shortening (do not use butter, margarine, spread or oil) in small microwave-safe bowl. Microwave at MEDIUM (50%) 1 minute; stir. If necessary, microwave at MEDIUM an additional 15 seconds at a time, stirring after each heating, just until chips are melted and mixture is smooth when stirred. Spoon melted chocolate over outside of flat-bottom ice cream cone. Refrigerate until chocolate is firm, about 30 minutes.
ORANGE FROSTING: Place 1/3 cup butter or margarine in microwave-safe bowl. Microwave at MEDIUM (50%) 1 minute or until melted. Stir in 2 cups powdered sugar, 2 teaspoons freshly grated orange peel and 1-1/2 teaspoons vanilla extract. Stir in 2 to 4 tablespoons hot water for desired consistency. Stir in red and yellow food color for desired color.
DECORATOR FROSTING: Combine 3 tablespoons water and 1 tablespoon meringue powder in small bowl. Add 1-1/2 cups powdered sugar and 1/8 teaspoon vanilla extract; beat on high speed of mixer until stiff. Stir in green food color for desired color.