Prepare the Baking Sheet:

1. Preheat oven to 400°F (200°C).
2. Line a rimmed baking sheet with parchment paper or aluminum foil, covering the sides for easy cleanup. Lightly grease the lining.
3. Arrange saltine crackers in a single layer, covering the entire surface.

2. Make the Toffee Layer:

1. In a medium saucepan over medium heat, combine butter and brown sugar.
2. Stir until the butter melts and sugar dissolves.
3. Bring to a rolling boil and cook for 3 minutes without stirring, until the mixture becomes a deep caramel color.

3. Assemble & Bake:

1. Carefully pour the hot toffee over the arranged crackers, spreading evenly.
2. Bake for 5-6 minutes, until the toffee is bubbly.

4. Add the Chocolate Layer:

1. Remove the baking sheet from the oven and immediately sprinkle chocolate chips over the hot toffee.
2. Let sit for a few minutes until the chocolate softens.
3. Use a spatula to spread the melted chocolate evenly over the toffee.

5. Add Toppings & Cool:

1. Sprinkle with chopped nuts, sea salt, or festive sprinkles (if using).
2. Allow to cool at room temperature, then transfer to the refrigerator for 1 hour until fully set.

6. Serve:

1. Once firm, break into bite-sized pieces using your hands or a sharp knife.
2. Enjoy immediately or store for later!