We suggest that you tint all icings while cake cools. Refrigerate tinted icings in covered containers until ready to use.
Make 5 1/2 cups buttercream icing:
Tint 2 1/2 cups green (thin 1 ¼ cups with 1 Tablespoon + ¾ teaspoon light corn syrup)
Tint 1/4 cup violet
Tint 1/4 cup orange (thin with ¾ teaspoon light corn syrup)
Tint 1/4 cup yellow
Reserve 2 1/4 cups white
Make 1/2 cup chocolate buttercream icing or use 1 can Wilton Chocolate Ready-To-Use Decorator Icing; tint black
Decorate in Order
Ice sides and background areas smooth with thinned green icing.
Use tip 3 and black icing to outline and pipe-in eyes and mouth (smooth with finger dipped in cornstarch.
Use tip 18 and white icing to cover ghost with stars.
Use tip 3 and violet icing to outline mask.
Use tip 6 and violet icing to pipe-in mask (smooth with finger dipped in cornstarch).
Use tip 3 and yellow icing to outline and pipe-in band on hat (smooth with finger dipped in cornstarch).
Use tip 16 and black icing to cover hat with stars.
Use tip 104 and black icing to pipe ruffle brim on hat.
For candy bag, trim 1/2 in. off graham cracker, ice smooth with orange icing. Position on cake and use tip 3 and black icing to print message.
Fill graham cracker candy bag with assorted Halloween candies.
Insert black shoestring licorice in hands for bag handle.
Use tip 18 and green icing to pipe rosette bottom border.
Preheat oven to 350°F or temperature per recipe directions. Your cake will unmold easily, without sticking, when you prepare the pan properly. Grease the inside of the pan using a pastry brush and solid vegetable shortening (do not use butter, margarine or liquid vegetable oil). Spread the shortening so that all indentations are covered. Sprinkle about 2 Tablespoons flour inside pan and shake so that flour covers all greased surfaces.
Turn pan upside down and tap lightly to remove excess flour. If any shiny spots remain, touch up with more shortening and flour to prevent cake from sticking. (You can use vegetable oil pan spray or vegetable oil pan spray with flour or use Wilton Cake Release, for perfect, crumb-free cakes!).
Make one 2-layer cake mix according to package or recipe directions. Pour the cake batter into pan, and if necessary, spread the batter around with a spatula to fill all areas of pan evenly. Be careful not to touch sides or bottom of pan.
Bake cake on middle rack of 350°F oven for 30-40 minutes or until cake tests done according to recipe directions.
Remove cake from oven and cool on cake rack for 10 minutes. While the cake is still in the pan, carefully slice off the raised center portion of the cake. This allows the cake to sit more level and helps prevent cracking.
To remove cake from pan, place cooling rack against cake and turn both cake rack and pan over. Lift pan carefully. Cool cake at least one hour. Brush loose crumbs off cake.
To transfer cake to serving board, hold a cake board against cake and turn both cake and rack over. Lift off rack. Hold another board against bottom of cake and turn cake over. Be sure to hold cake, rack and board close together while turning to prevent cake from cracking.