Line a baking sheet with aluminum foil and spray with nonstick cooking spray.
On the baking sheet, arrange crackers in a single layer leaving no empty spaces. Crush any remaining crackers into small crumbs and set aside.
In a small saucepan over medium-high heat, place butter and brown sugar. Stir while butter melts; bring mixture to a rolling boil. Once boiling, carefully pour the sugar-butter mixture over crackers on the baking sheet in an even layer, trying to cover most of the crackers. Bake toffee crackers at 350ºF (180ºC) for 5 minutes, until the toffee is bubbling all over. Carefully remove pan from oven and cool for 1 minute.
On top of hot toffee, sprinkle chocolate chips; let sit for 1 minute. Once softened, use an offset spatula or knife to spread the melted chocolate in an even layer over entire surface of the toffee. While the chocolate is still sticky, sprinkle the top with the rest of crushed crackers.
Refrigerate for 30 minutes. Once set, break into small pieces by hand.