an 8-by-2-inch round baking pan; a skewer (optional); 5 piping bags; a plain 1/2-inch round decorator piping tip; 2 large open star decorator pipping tips; 2 large closed star decorator piping tips; kitchen-dedicated shears
For the cake: Preheat the oven to 350 degrees F. Coat an 8-by-2-inch round baking pan with flour-based baking spray.
In a large bowl, whisk together the flour, baking powder, salt and baking soda. Add the water, granulated sugar, oil, vinegar and vanilla. Mix on low until combined.
Divide the batter among 3 bowls. Tint one bowl with the red food color, one bowl with the orange and one with the yellow. Pour half of each color of batter alternately in the prepared baking pan, then continue with the remaining batter, alternating colors. Swirl the colors together using a skewer or butter knife. Bake the cake until the center springs back when pressed in the center, 30 to 35 minutes. Remove the cake from the pan to a wire rack to cool completely.
Using a serrated knife or cake leveler, level the cake and reserve the scraps. Cut the leveled cake layer in half.
For the buttercream frosting: In the bowl of an electric mixer fitted with the whip attachment, beat the butter until fluffy. Add the confectioners' sugar and mix on low speed until just combined. Increase the mixer speed and add the vanilla and milk or cream one tablespoon at a time until the mixture thins to piping consistency.
Spread about 1/4 cup of the frosting on one half of the cut cake layer and top with the second half. Set aside.
Crumble the cake scraps in a bowl using your fingers. Add 2 to 3 tablespoons of frosting to the scraps and mix well using your hands. Place about 5 tablespoons of the cake mixture on a parchment-lined baking sheet and form it into a small baton shape with one rounded end for the turkey's head and neck. Refrigerate to chill, about 15 minutes. (The leftover cake mixture can be used for cake pops.)
Fit a piping bag with a plain 1/2-inch round decorator piping tip. Fit 2 piping bags with large open star decorator piping tips. Fit 2 piping bags with large closed star decorator piping tips.
Divide the remaining frosting into 5 separate bowls. Tint one bowl with the red food color, another bowl with the orange and another bowl with the yellow. Combine another bowl of frosting with the cocoa powder to create a pale tan color and mix the melted chocolate with the last bowl to create chocolate frosting.
Transfer the red bowl of frosting to the piping bag fitted with the plain 1/2-inch round tip. Transfer the yellow and orange frostings into each of the piping bags fitted with the large open star tips. Transfer the light tan and chocolate frostings into each of the piping bags fitted with the large closed star tips.
For the assembly: Dip the chilled head and neck piece in the melted chocolate chips and place on the parchment-lined baking sheet using 2 forks. Chill until firm, about 15 minutes. Reserve the leftover melted chocolate for later use.
Using the piping bag filled with the red frosting, pipe 1-inch dots of frosting around the top rounded edge of the cake. Place the bowl of a spoon in the center of each dot and pull the frosting down toward the bottom flat edge of the cake.
Using the piping bag filled with the tan frosting, pipe shells in a downward motion that overlap the red frosting layer. Use a spoon to remove some of the bottom edge of the shell row to make room for the next layer.
Using the piping bag filled with the chocolate frosting, pipe shells in a downward motion that overlap the tan shell layer. Use a spoon to remove some of the bottom edges of the shell row to make room for the next layer.
Using the piping bag filled with the yellow frosting, pipe shells in a downward motion that overlap the chocolate frosting layer, but do not remove any of the frosting using a spoon as with the previous rows.
Using the piping bag filled with the orange frosting, pipe a final layer of shells at the bottom center of the cake. Remove the chocolate-covered cake piece from the refrigerator and place it in the middle center of the cake. Turn the cake upright so that it sits on its flat cut edge. Using the piping bag filled with chocolate frosting, pipe a shell border on the top edge of the cake so that the shell tips point to the unfrosted side. Using the piping bag filled with the orange frosting, pipe a row of shells that overlaps the row of chocolate frosting shells. Using the piping bag filled with yellow frosting, pipe a row of shells that overlaps the orange frosting. Finish the back of the cake by piping rows of shells using the tan frosting.
Reheat the reserved melted chocolate if necessary. Dip the candy bead into the chocolate and adhere to the turkey's head. Cut the lemon chew in half so that you have 2 triangles. Use the back of a small knife to score a line onto one of the triangles, from the pointed triangle end to the cut edge. Use a small brush to cover the cut edge of the candy with melted chocolate and press onto the rounded edge of the chocolate-covered cake piece to form a beak.
Cut a large teardrop-shaped piece from the fruit tape using kitchen-dedicated shears and peel away the backing. Adhere it to the candy chew with chocolate so that it falls behind the beak. Cut a smaller teardrop-shaped piece from the fruit tape and adhere with chocolate, so that it falls in front of the beak. Let stand until set, about 10 minutes.
Place the gingersnaps on a baking sheet. Dip the backs of the candy corn pieces into the melted chocolate and arrange 3 on one side of each gingersnap. Let stand until set, about 10 minutes. Insert each cookie upright into the top of the cake so that the candy corn pieces are showing to the front of the turkey.