Preheat your oven to 350°F (175°C). Prepare the devil's food cake mix according to the package instructions, then pour the batter into a greased 9x13 inch baking dish. Bake it for the time specified on the box, usually around 30-35 minutes, or until a toothpick inserted in the center comes out clean.
Once the cake is baked and still warm, use the handle of a wooden spoon to poke holes all over the top of the cake. This step is crucial as it allows the sweetened condensed milk and caramel sauce to seep into the cake, making it incredibly moist.
Pour the entire can of sweetened condensed milk over the warm cake, ensuring it fills the holes you poked. Let it sit for about 10 minutes to soak in.
Next, drizzle the caramel sauce over the cake, allowing it to create a beautiful, gooey layer on top. Use as much or as little as you like—there’s no such thing as too much caramel!
Allow the cake to cool completely at room temperature. Once it’s cool, cover it and place it in the refrigerator for at least an hour, or until you are ready to serve it.
Once chilled, spread the Cool Whip over the top of the cake evenly. This will create a light and fluffy contrast to the rich chocolate and caramel layers.
Finally, sprinkle the crushed Heath bars over the Cool Whip layer. This adds a delightful crunch and an extra layer of chocolatey goodness to your Better Than Anything Cake.