Preheat the oven to 350°F. Spray a 9X13 inch baking dish with non-stick cooking spray and set aside.
In a large bowl, mix together the yellow cake mix, pumpkin puree, brown sugar and pumpkin pie spice until combined and smooth but do not over mix. You can use a hand mixer here to make things easier.
15.25 ounces yellow cake mix, 15 ounces pumpkin puree, 2 tablespoons brown sugar, 1 teaspoon pumpkin pie spice
Transfer the cake batter to the prepared baking dish and spread evenly. Bake the cake for 20 to 25 minutes. An inserted toothpick should come out clean.
Allow the cake to cool for 15 minutes on a wire rack.
Poke holes all over the top of the cake about 1 inch apart and about halfway through the cake. You don't want to poke the holes through to the bottom of the cake. You can use the end of a wooden spoon or spatula to poke the holes.
Evenly pour the sweetened condensed milk over the top of the cake making sure it fills all of the holes you just created. Chill the cake in the fridge for 30 minutes to all the sweetened condensed milk to soak into the cake.
14 ounces sweetened condensed milk
Remove the cake from the fridge and carefully spread the whipped topping evenly over the top of the cake.
8 ounces frozen whipped topping
Sprinkle the Heath bits over the top. Next, drizzle the caramel sauce over the top of the cake. 1 cup caramel sauce, 1 cup toffee bits
Finally, place the cake back in the fridge and allow it to chill for a minimum of 3 hours. If you have the time, this cake is truly at it's best when it is make the day before and chilled overnight. Serve and enjoy!