Preheat oven to 350ºF. Line jelly roll pan or cookie sheet with foil and spray with non-stick spray. Lay a flat layer of crackers out on the foil. Melt the sugar and butter until a boil is reached. Reduce the heat and simmer, uncovered, for 5-6 minutes or until mixture is thickened and sugar is completely dissolved. Pour this mixture over the crackers and spread to coat evenly. Bake for 5-8 minutes, or until the toffee becomes bubbly. After removing the pan from the oven, let it sit for 3-5 minutes. Sprinkle on the chocolate chips, let them soften and melt, and then spread them into an even layer. (You can add nuts, cracker crumbs, or whatever else floats your boat at this point.) Let cool and, if desired for expediting purposes, refrigerate until hardened. Break into pieces the size of your choice.