Preheat oven to 350 degrees F. Line a 9x13-inch baking pan with foil. Spray the foil with non-stick cooking spray.
Arrange the saltine crackers in a single layer on the bottom of the prepared pan. Break the crackers in half if necessary to fit around the edges.
Place the butter in a medium heavy-bottomed saucepan and melt over medium heat. Once the butter has melted, add the brown sugar and bring to a boil, stirring constantly. Boil for 3 to 4 minutes, or until the sugar has completely dissolved. Remove from the heat and immediately pour evenly over the saltine crackers. Use an offset spatula to spread it, ensuring that all of the crackers are coated.
Bake for 8 to 10 minutes, or until bubbling. Remove from the oven and immediately sprinkle the chocolate chips evenly over the mixture. Allow the chocolate chips to soften for 3 to 5 minutes, then use an offset spatula to spread the chocolate into an even layer. Sprinkle with the chopped pecans.
Cool at room temperature for 15 to 30 minutes, or until the pan is able to be handled easily, then refrigerate for 1 hour, or until the chocolate is set. Break into pieces and store in an airtight container at room temperature for up to 2 weeks.