Line 1 large or 2 small jelly-roll pans with aluminum foil, spray with nonstick spray and arrange the saltines salt-side down in a single layer. In a medium saucepan, melt the butter and brown sugar together and boil until it turns a caramel color, a few minutes. Remove from the heat and pour over the crackers, covering them evenly.
Put the jelly-roll pan into the oven and bake for 3 to 5 minutes, or until just bubbly, watching carefully. Remove from the oven and pour the chocolate chips over the crackers. When the chips melt a bit, spread them over the crackers with a knife.
Transfer the pan to the freezer for 15 to 20 minutes, or until completely cold. They will form one big sheet. Break up into pieces. Store in an airtight container.
*Percent Daily Values are based on a 2000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.