Line a large baking sheet with aluminum foil, making sure the foil extends slightly up the sides for easy removal later.
Arrange the graham cracker squares in a single, even layer on the prepared baking sheet, covering as much surface area as possible. Set aside.
In a medium saucepan set over medium heat, combine the butter and brown sugar. Stir constantly as the butter melts and the mixture comes to a rolling boil.
Once boiling, continue cooking and stirring for about 2 minutes, until the mixture thickens slightly and looks smooth and glossy.
Remove the saucepan from the heat and immediately stir in the chopped pecans until evenly coated.
Carefully spoon and spread the hot pecan mixture over the graham crackers, making sure it reaches all the edges and covers the crackers evenly.
Transfer the baking sheet to the refrigerator and chill until the topping is completely set and firm.
Once hardened, break or cut into pieces and serve.
Enjoy!
