Preheat oven to 350 degrees F (175 degrees C). Line a jelly roll pan with aluminum foil.
Melt butter and margarine together in a saucepan; stir brown sugar into butter mixture until dissolved; bring to a boil, reduce heat to medium, and cook at a boil until caramelized, about 2 minutes.
Spread graham crackers in a single layer onto prepared aluminum foil.
Pour butter mixture over graham crackers.
Sprinkle pecans over the crackers.
Bake in preheated oven until topping begins to solidify, about 12 minutes.
Let crackers cool before breaking into pieces to serve.
