Prepare Icing We suggest that you tint all icings at one time while cake cools. Refrigerate tinted icings in covered containers until ready to use.
Make 4 3/4cups buttercream icing: Tint 1/2 cup ivory
Tint 1/2 cup rose
Tint 1 cup green
Tint 1/2 cup violet
Tint 3/4 cup blue
Tint 1 1/2 cups grey (thin with 1 tablespoon and 1 1/2 teaspoons light corn syrup)
Decorate in Order
Insert doll pick in cake. Ice cake smooth with thinned gray buttercream icing.
Spatula ice fluffy water with blue buttercream icing.
Using tip 12, pipe a mound of icing for torso. Using tip 101, overpipe mound with ruffle scales in green buttercream. Begin at bottom of the tail and overlap each row slightly.
Spatula stripe decorating bag with ivory and rose icing colors. Using tip 199, pipe shells on cake and for mermaid suit in ivory/rose buttercream.
Using tip 3, print name in rose buttercream. Using tip 3, outline straps in green buttercream.
Using tip 233, pipe pull-out grass sea grass in violet buttercream.
Using tip 225, pipe drop flowers on cake and in hair in rose buttercream. Using tip 2, add dot centers in ivory buttercream.
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 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, in place of solid shortening and flour, or use New 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 the pan evenly. Be careful not to touch sides or bottom of pan.
Bake cake on middle rack of 350 F oven for 70-85 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 off 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.