Preheat oven to 350 degrees F. Spray a 9x13 baking dish with cooking spray.
Whisk together pumpkin, both sugars, spices, salt, cornstarch, eggs and milk.
In a separate bowl, stir together cake mix, pecan chips and toffee bits. Stir into pumpkin mixture.
Pour cake batter into prepared baking dish. Pour butter evenly over top of cake batter. Bake for 1 hour. Serve warm with ice cream, whipped topping or a drizzle of caramel syrup.
Notes
For a crunchy topping, toffee bits and pecans can be sprinkled over the top of the batter (before adding butter) instead of mixed in with the cake mix.
For a more cobbler-like dessert, use half or ¾ of the cake mix instead of the entire thing.
If you can’t find toffee bits, you can chop up Heath Bars or Skor Bars in a food processor.
If using a dark metal pan or glass pan, reduce oven temperature to 325 degrees. You may need to lengthen the baking time a little bit, so keep an eye on it.