Preheat oven according to package directions. Coat three 9-inch circular springform pans with cooking spray. If you do not have three pans, bake one at a time.
In a large mixing bowl or the bowl of a stand mixer, prepare both packages of yellow cake mix according to package directions, but reducing WATER BY 75%. For mine, it called for 2 cups, I used 1/2 cup. Fold in diced apples.
Bake according to package directions or until top is golden brown and it passes the toothpick test. Remove and allow to cool to room temperature.
Trim cakes, if needed, to lie flat. Place the first cake on serving platter. Frost liberally, sprinkle with chopped SNICKERS® and a drizzle of caramel syrup. Continue with the next two layers.
Frost entire cake with a thin crumb catcher layer of frosting, refrigerate for a minimum of 30 minutes.
Complete frosting evenly. Refrigerate again.
Melt white and milk chocolate in a bowl or candy bags. Making two passes with both, drizzle on just the edges of the cake, coming about 1 inch into the top. The cold frosting should make the chocolate harden upon contact. Finish with caramel drizzle coming about 2 inches in. Mound remaining SNICKERS® in the center. Refrigerate until ready to serve. Drizzle with extra caramel, if desired.
While I used box mixes and pre-made frosting, feel free to use your own homemade recipe.I use baking strips for even baking instead of leveling each cake. These can be purchased at any baking or craft store. You can also cut a thick kitchen towel to the right specifications, soak it in water and then secure it with safety pins.