Preheat your oven to 350 degrees Fahrenheit. Line a large rimmed baking sheet with aluminum foil and then place a layer of parchment paper on top of the foil. This double lining is essential because the toffee becomes very sticky and this makes cleanup a breeze. Arrange the saltine crackers in a single, tight layer on the parchment paper, breaking some in half if necessary to fill the gaps.
In a medium saucepan over medium heat, combine the unsalted butter and the packed brown sugar. Stir constantly until the butter is completely melted. Bring the mixture to a rolling boil and let it cook for exactly three minutes without stirring. This timing ensures the sugar reaches the correct stage to set into a firm toffee. Remove from heat and immediately stir in the alcohol-free vanilla extract.
Carefully pour the hot toffee mixture over the layer of crackers on the baking sheet. Use a spatula to spread it evenly so that every cracker is completely coated. Place the baking sheet in the oven and bake for 5 to 7 minutes, or until the toffee is bubbling across the entire surface. Keep a close eye on it to ensure the edges do not burn.
Remove the pan from the oven and immediately sprinkle the chocolate chips evenly over the hot toffee. Let the pan sit for about 2 to 3 minutes until the chocolate chips have softened and become glossy. Use an offset spatula or the back of a spoon to spread the melted chocolate into a smooth, even layer across the top.
While the chocolate is still wet, sprinkle your holiday decorations and sea salt over the top. Let the pan sit at room temperature for 30 minutes, then transfer it to the refrigerator for at least 2 hours to fully set. Once the chocolate and toffee are firm, it is ready to be peeled away from the parchment and broken into rustic pieces or cut with a sharp knife into neat squares.
