Preheat oven to 400°F (200°C) and line a baking sheet with parchment paper or a silicone mat.

Arrange saltine crackers in a single layer on the prepared baking sheet, ensuring they are tightly packed.

In a medium saucepan, combine butter and brown sugar over medium heat; stir until the butter is melted.

Bring the mixture to a boil and cook for exactly 3 minutes without stirring.

Immediately pour the toffee mixture over the crackers and spread evenly using an offset spatula.

Bake in the preheated oven for 5 minutes until the toffee is bubbling across the entire surface.

Remove from the oven and sprinkle the chocolate chips evenly over the hot toffee.

Let sit for 2 minutes until the chocolate is softened, then spread the chocolate into an even layer.

Top with chopped pecans or festive sprinkles while the chocolate is still wet.

Allow to cool completely at room temperature, then refrigerate for at least 1 hour before breaking or cutting into pieces.