Preheat oven to 350 degrees. Prep a 13x9 inch metal baking pan with nonstick baking spray.
Prepare brownies as per the package instructions on the back of the box. Bake at 350 degrees for half of the baking time listed.
1 box of brownie mix
In a large bowl, use an electric mixer to combine butter, sugar, corn syrup, eggs, and vanilla until completely mixed.
1 cup white sugar, 1 ½ cups light corn syrup, 4 eggs, ¼ cup butter, 1 ½ tsp vanilla extract
Use a large spoon to add the chopped pecans.
2 cups chopped pecans
Remove the brownies from the oven.
Spoon the pecan pie mixture on top of the brownies.
Use an offset spatula even the top layer of the filling.
Return the brownies to the oven.
Continue to bake at 350 degrees for 25 to 35 minutes. (The filling will jiggle in the middle as you move the baking pan.)
Take out of the oven.
Set aside to cool completely and serve.