1. Preheat oven to 350°F. Following package instructions, make the cake using the vegetable oil and eggs. Replace the water with carrot juice. Fold the shredded coconut and chopped walnuts into the batter. Spray 2 (9-inch) round cake pans liberally with baking spray and divide the batter evenly between the pans. Bake according to package directions.
2. To make the frosting, bring 1 inch of water in a saucepan to a simmer. Place a heatproof bowl over the simmering water and add the chocolate. Stir for 3–4 minutes or until melted. Remove from heat and add frosting. Mix until well combined. Remove the cakes from the oven and cool 10 minutes on a baking rack. Remove cakes from pans and let cool completely.
3. Frost the top of one cake layer with about 1/2 cup frosting and set the other half on top. Frost the top and sides of the cake with the remaining frosting. Arrange the KitKat bars along the side of the cake, trimming if they are too tall. Decorate the top with M&Ms and Reese’s Pieces.
Per serving: 808 calories, 43g fat, 17g saturated fat, 50mg cholesterol, 425mg sodium, 96g carbohydrate, 3g fiber, 50g sugar, 9g protein