Sailboat Cake

One-Bowl Chocolate Cake:

Preheat oven to 350 degrees. Butter two 8-inch square cake pans, and line bottoms with parchment; butter parchment, and dust with cocoa.

Into the bowl of an electric mixer fitted with the paddle attachment, sift cocoa, flour, sugar, baking soda, baking powder, and salt. With the mixer on low, stir in eggs, 1 1/2 cups warm water, buttermilk, vegetable oil, and vanilla until smooth, about 3 minutes.

Divide batter among prepared pans. Bake, rotating once, until tester inserted in center comes out clean, 35 to 45 minutes.

Let cakes cool in pans on a wire rack for 20 minutes, then remove from pans and cool completely, right side up on rack. Cakes can be made in advance and stored up to 1 day in refrigerator. They can be stored 1 week in the freezer.

Using a serrated knife, trim the tops of both cake layers to be level. Brush away excess crumbs. Place the bottom layer on an 8-inch cardboard square. Add food coloring, one drop at a time, to the frosting, and mix until desired color. Spread 1 1/2 to 2 cups tinted frosting over the top of the bottom layer. Top with the second layer, cut side down. Spread 2 cups frosting in a thin layer over the entire cake.

Seven-Minute Icing:

In small heavy saucepan over medium heat, heat 2 cups sugar, the corn syrup, and 2/3 cup water, stirring occasionally, until sugar has dissolved. Wash down sides of pan with pastry brush dipped in water to keep crystals from forming. Increase heat to high; bring to boil without stirring. Cook until mixture is 235 degrees on candy thermometer.

While syrup cooks, place egg whites in bowl of an electric mixer fitted with whisk attachment. Whip on medium speed until frothy. When syrup in pan has reached 235 degrees, pour hot syrup into egg whites in a slow, steady stream down side of bowl. Increase mixer speed to medium-high; whip until fluffy and cool, 7 to 10 minutes. Add vanilla; whisk well. Tint with food coloring.

Using serrated knife, trim tops of both cake layers to be level. Brush away excess crumbs. Place bottom layer on 8-inch cardboard square. Spread 1 1/2 to 2 cups icing over top of bottom layer. Top with second layer, cut side down. Spread 2 cups icing over cake in thin layer.

Place the assembled cake on inverted cake pan to raise the bottom edge for easier decorating. Use a large offset spatula to generously cover all of the cake with more icing. Use the long edge of the spatula to smooth the frosting on each side.

Press cake-decorating comb into sides to make vertical lines around the cake, dividing each side into four equal parts; these guides will help you keep the waves even and neat. Pull comb or serrated knife across sides, making a U shape from one line to the next to form waves.

On top of cake, use a small offset spatula to pull the still-moist frosting straight up, creating frothy waves. Press decorated fish cookies into sides of cake; icing will help them stick. Place paper sailboat on top of cake. Serve slices of the cake with more fish cookies on the side.