Preheat the oven to 400℉. Line a baking sheet with parchment paper sprayed with nonstick cooking spray. Arrange the crackers in a single layer, covering the baking sheet.
In a saucepan, combine the butter and sugar. Stirring frequently, bring the mixture to a boil for 3 minutes. Remove from heat and immediately pour over the saltines, spread it to the edges to evenly coat. Bake for 5 to 6 minutes.
Remove from the oven and sprinkle with the chocolate chips. Allow to cool on the counter for 5 minutes, then spread the melted chocolate chips evenly across the toffee. Top with chopped pecans and allow to cool completely before breaking into toffee pieces.