Line an 11x17 pan with foil and grease the foil well. Line with crackers.
In a medium saucepan, combine butter and brown sugar. Bring to a boil over medium heat and let come to a rolling boil for 3 minutes. DO NOT STIR.
Pour brown sugar mixture over the crackers. Bake 4 minutes.
Pour chocolate chips over the top and let sit 4 minutes or until chocolate is soft (or place 1 minute in the warm oven). Spread chocolate evenly and sprinkle pecans on top.
Cool on the counter slightly and then place into the freezer to cool completely. Break into pieces.