Preheat oven to 425 F. Line a rimmed cookie sheet with aluminum foil. Fill sheet with all 40 saltine crackers in a single layer.

In a medium saucepan over medium-high, melt butter and brown sugar together and bring to a boil. Stir occasionally until combined and sugar is melted. Continue to boil undisturbed for 5 minutes.

Remove from heat and pour caramel mixture over the cracker layer. Spread with a wooden spoon if needed to cover them evenly.

Bake in preheated oven for 4-5 minutes, or until just bubbly.

Remove from oven and sprinkle immediately with chocolate chips. When chips begin to melt, spread them over crackers with an icing spatula. If you plan on adding any topping, add them on at this point while the chocolate is still melted.

Transfer pan to refrigerator until firm, about 2 hours. Break into pieces and store in an airtight container.