Preheat the oven to 325°F.
Prepare the brownie mix according to the package directions.
Pour the batter into a greased baking dish and par-bake for 12 minutes.
While the brownies are baking, prepare the pecan pie filling.
Melt the butter in a saucepan over medium heat.
Once melted, stir in the sugar and corn syrup until well combined.
Quickly whisk in the eggs, then bring the mixture to a gentle boil.
Stir in the vanilla.
Continue cooking until the filling has thickened enough to coat the back of a spoon.
Stir in the pecans.
Carefully pour the pecan pie filling evenly over the brownies and return the dish to the oven.
Bake for an additional 15 minutes.
Remove from the oven when the filling still has a slight jiggle in the center.
Allow the brownies to cool completely, giving the pecan pie filling time to set.
Once cooled and set, slice and serve.