Preheat oven to 350°F. Line 3 9-inch round cake pans with parchment paper and spray the sides with baking spray. Set aside.
Add all of the ingredients for the chocolate cake mix batter indicated on the back of the box as well as the additional cocoa to a large mixing bowl. Whisk together until fully combined. Pour the cake batter into one of the prepared cake pans just until ¾ full. You will not use all of the cake batter. Set aside.
15.25 ounces chocolate cake mix, 1¼ cups water, ⅓ cup vegetable oil, 3 large eggs, ¼ cup unsweetened cocoa powder
To make a caramel cake layer, add all of the ingredients indicated on the back of the box plus the caramel sauce and caramel extract to a large mixing bowl. Whisk together until fully combined. Pour the cake batter into a prepared cake pan just until ¾ full. You will not use all of this cake batter. Set aside.
15.25 ounces yellow cake mix, 1 cup water, ½ cup vegetable oil, 3 large eggs, 3 tablespoons caramel sauce, 1 teaspoon caramel extract
To make the vanilla cake layer, add all of the ingredients indicated on the back of the box plus the vanilla bean paste to a large mixing bowl. Whisk together until fully combined. Pour the cake batter into the prepared cake pan until ¾ full. You will not use all of this cake batter either.
15.25 ounces white cake mix, ½ cup vegetable oil, 3 large eggs, 1 teaspoon pure vanilla extract, 1 cup water
Place all of the cakes into the oven to bake for 30 minutes or until a toothpick inserted into the center of each of them comes out clean or with moist crumbs. Once baked, remove from the oven and place them onto a cooling rack to cool completely to room temperature.
To make the vanilla frosting, add all of the frosting ingredients to the bowl of a stand mixer fitted with a paddle or whisk attachment. Beat together on high-speed for 1-2 minutes or until a fluffy and smooth frosting has formed. Fill a piping bag fitted with a round tip ¾ full with frosting. If you want a naked cake look, simply halve the frosting recipe.
2 cups unsalted butter, 4½ cups powdered sugar, 1 teaspoon pure vanilla extract, ½ teaspoon kosher salt
To make the chocolate ganache, heat the heavy cream in a microwave-safe bowl for 1 minute. Pour the heated heavy cream over the chocolate chips and let set for 1 minute. Mix the chocolate chips and heavy cream together until smooth and chocolate ganache has formed. Add in the corn syrup and mix until well combined.
½ cup chocolate chips, ¼ cup heavy cream, 2 teaspoons corn syrup
Place the cooled chocolate cake layer onto a cake stand or serving platter. Pipe a border of frosting around the top edge of the cake. Spoon the chocolate ganache into the center of the frosting wall and spread to the inside edges.
Place the caramel cake layer on top of the chocolate cake layer ensuring that the edges line up. Pipe a border of frosting around the top edge of the caramel cake. Pour the caramel sauce into the center of the frosting wall spread to the edges.
⅓ cup caramel sauce
Place the vanilla cake layer on top of the caramel cake layer ensuring that the edges line up. Use an offset spatula or rubber spatula to frost the top and sides of the cake with the remaining frosting. If you so desire, pipe a decorative edge all around the bottom of the cake. You can also drizzle chocolate and caramel sauce over the top of the cake for a decorative touch.