In a large bowl blend together the cake mix, eggs, water, and melted butter until smooth.
Spray the slow cooker with cooking spray, then add the batter. Smooth into an even layer.
Cover and cook on high for 2 hours without opening the lid during cooking.
When done, use the end of a spoon to poke holes in the cake. Then pour over condensed milk and 1⁄2 cup of caramel topping. Remove the slow cooker insert and sit aside to cool.
When the bottom of the insert is cool to the touch, place the cake into the refrigerator for at least 2 hours or overnight.
Once chilled, spread the whipped topping evenly over the cake. Then sprinkle the chopped Heath bar over top and drizzle over the carmel and chocolate topping.
Serve by scooping out the cake with a large spoon. Enjoy!
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Notes
I like using the extra creamy Cool Whip, but you can also substitute homemade whipped cream for whipped topping.
Other toppings can include chocolate chips, almonds, toffee bits, or Heath Bits.
Other chocolate cake mixes can be substituted for the Devil's Food cake mix.
Leftovers should be covered and refrigerated for up to 3-4 days.
You can also freeze this cake in an airtight container for up to three months.