Step 1Simmer half-and-half, cocoa powder, and kosher salt in a small saucepan over medium heat, stirring constantly, until smooth, 4 to 5 minutes. Remove from heat and stir in bittersweet chocolate until smooth. Let cool 5 minutes.

Step 2Beat butter and powdered sugar on medium speed until fluffy, 2 to 4 minutes. Gradually add chocolate mixture and beat until smooth, 1 to 2 minutes more.

Step 3Level tops of each cake with a serrated knife to create even layers. Place down one cake and top with a heaping cup of frosting, then top with second cake and repeat with third layer.

Step 4Using about 1 1/2 cups of frosting, smooth a crumb coat around outside of the cake. Transfer cake to refrigerator until frosting is hardened, 30 minutes to 1 hour.

Step 5Meanwhile, make the white chocolate turkey tail feathers: Heat white chocolate in a medium heatproof bowl set over a medium pot of barely simmering water (bottom of bowl should not touch water), stirring occasionally, or in short bursts in the microwave, stirring in between bursts, until chocolate is melted and smooth. Repeat this with all colors.

Step 6Dip clean, dry pastry brush into melted chocolate. Brush a stripe of chocolate that resembles a turkey tail feather on a parchment-lined baking sheet. Chill. Repeat process with all chocolate colors on second parchment-lined baking sheet.

Step 7Swap trays and go over original brush strokes, repeating and chilling in between coatings. Gently reheat chocolate if needed, until feathers are 1/4" thick. Use this technique to create a turkey beak and wattle that you will place near the beak.

Step 8Spread remaining frosting all over cake using an offset spatula, creating a feathered pattern.

Step 9Place Oreo halves on front side of cake, icing side up for eyes. Dot the bottom of chocolate M&Ms with frosting and place on top of Oreo halves for eyeballs.

Step 10Place colorful, feathers on the top of the cake for the tail. And the smaller white ones on each side for the wings.

Step 11Finish by placing the beak and wattle right below the eyes.