Preheat the oven to 350 F degrees and grease a 9"-x-13" pan with cooking spray.
Prepare the butter pecan cake mix according to package instructions. Pour the batter into the prepared pan and bake until the cake is golden and a toothpick inserted into the center of the cake comes out clean. Should take about 30 minutes.
Using the handle of a wooden spoon, poke holes into the cake across the entire surface. Microwave the jar of dulce de leche for about 30 seconds, then stir it around, make sure it's pour-able. Pour the dulce de leche over the top to fill the holes.
Spread the cool whip or whipped cream over the top of the cake and garnish with the pecans and toffee bits.
Slice into squares and serve.
If you can't find butter pecan cake mix, white cake mix will work. Substitute melted butter for vegetable oil.Dulce de leche is a thick caramel sauce made with sugar and milk. It can be substituted for caramel mixed with condensed milk.If you don't like cool whip then substitute with equal amounts of whipped cream.Please keep in mind that nutritional information is a rough estimate and can vary greatly based on products used.