1. Heat oven to 350°F. Grease and flour 13 x 9 x 2-inch baking pan.
2. Place peanut butter chips and shortening in small microwave-safe bowl. Microwave at HIGH (100%) 1 to 1-1/2 minutes or until smooth when stirred. Prepare cake mix as directed on package with water, eggs and oil; blend in melted chip mixture. Pour batter into prepared pan.
3. Bake 30 to 35 minutes or until wooden pick inserted in center comes out clean. Cool 10 minutes; remove from pan to wire rack. Cool completely.
4. Cut cake as directed on diagram. Frost top and sides of Piece A with vanilla frosting; place on large serving plate or tray. Using leaf tip and green decorator icing, make tree branches about 1-1/2 inches long, starting at bottom of tree. Press holiday bits onto top of cake; lightly press into branches.
4. Frost top and sides of Piece B with brown decorator icing for trunk; attach to bottom of tree. Frost top and sides of Piece C with red decorator icing for pot; attach to bottom of trunk.
5. Frost other pieces with vanilla frosting for packages. Decorate with strands of Pull 'N' Peel and holiday bits, as desired. 12 to 15 servings.