Preheat your oven to 400°F (200°C). Line a half-sheet baking pan with aluminum foil and spray it lightly with nonstick cooking spray.
Lay out the saltine crackers in a single layer on the prepared pan, with their salted side facing up. Make sure they are touching each other to form a solid base.
In a medium saucepan, combine the butter and brown sugar. Heat over medium heat, stirring constantly with a whisk, until the mixture reaches a full, rolling boil (it should keep bubbling even when stirred). Once boiling, stop stirring and let it continue to boil gently for exactly 3 minutes. It's important to keep the heat low enough to maintain a constant, gentle boil for the best texture.
Carefully pour the hot toffee mixture all over the arranged saltine crackers. Use the back of a spoon to gently spread it if necessary, ensuring all crackers are covered.
Place the pan in the preheated oven and bake for just 5 minutes.
Immediately remove the pan from the oven and sprinkle the chocolate chips evenly over the hot toffee. Let them sit undisturbed for about 5 minutes to soften from the residual heat.
Gently spread the melted chocolate chips into a smooth layer over the toffee. Now's your chance to get creative! Sprinkle with festive sprinkles, chopped nuts, or any other optional toppings for a beautiful finish.
Allow the candy to cool completely until it's firm. You can pop it in the refrigerator for a quicker set. Once fully hardened, simply break or cut the large sheet into delicious, bite-sized pieces. Enjoy your irresistibly easy Christmas treat!