Begin by preheating your oven to 350°F (175°C). Line a large baking sheet with parchment paper, ensuring there’s enough overhang on the sides to facilitate easy removal of the finished product.
Next, arrange the Saltine crackers in a single, even layer across the parchment-lined baking sheet, completely covering the surface.
In a medium saucepan set over medium heat, melt the unsalted butter. Once the butter is fully melted, add the packed brown sugar, stirring continuously until the mixture reaches a gentle boil. Allow it to boil undisturbed for 2-3 minutes.
Carefully pour the hot toffee mixture evenly over the arranged Saltine crackers. Use a spatula to gently spread the toffee to ensure all the crackers are fully covered.
Place the baking sheet in the preheated oven and bake for 5-6 minutes. You want the toffee to be bubbly and golden during this time.
Once baked, remove the sheet from the oven and immediately scatter the semi-sweet chocolate chips evenly over the hot toffee layer. Let them sit for a few minutes to soften and melt.
After a few minutes, take a spatula and gently spread the melted chocolate over the toffee until it’s evenly coated. If desired, sprinkle the chopped nuts on top along with a light pinch of sea salt to enhance the flavor.
Allow the toffee to cool at room temperature until it is firm. For quicker results, you can place it in the refrigerator for about 30 minutes.
Once the toffee is completely cooled and set, break it into pieces of your preferred size. Serve immediately or store the pieces in an airtight container for later enjoyment.