Preheat your oven to 350 degrees Fahrenheit. Line a large rimmed baking sheet with parchment paper or a silicone baking mat to ensure the toffee does not stick. Arrange the saltine crackers in a single layer on the prepared pan, side by side, until the entire surface is covered.
In a medium saucepan, combine the butter and light brown sugar over medium heat. Stir constantly until the butter is melted and the mixture begins to boil. Once it reaches a boil, let it bubble for exactly three minutes without stirring. Remove the pan from the heat and carefully stir in the alcohol-free vanilla.
Carefully pour the hot toffee mixture evenly over the arranged crackers. Use a spatula to spread it quickly before it sets, making sure every cracker is well coated. Place the baking sheet in the oven and bake for 8 to 10 minutes, or until the toffee is bubbling across the entire pan.
Remove the pan from the oven and immediately sprinkle the chocolate chips over the hot toffee. Let them sit for about 5 minutes until they are soft and shiny. Use an offset spatula to spread the melted chocolate into an even layer across the top of the toffee.
While the chocolate is still wet, sprinkle the chopped pecans and a pinch of sea salt evenly over the top. Allow the pan to cool to room temperature, then place it in the refrigerator for at least 2 hours to fully set. Once firm, break the toffee into irregular pieces by hand or use a knife to cut it into squares.
