Preheat oven to 375°F (190°C). Line a large 10x15-inch rimmed baking sheet with heavy-duty aluminum foil or parchment paper, spraying lightly with nonstick spray. Arrange the saltine crackers in a single snug layer across the pan.

In a medium heavy-bottomed saucepan over medium heat, melt the butter and brown sugar together. Bring to a rolling boil and let boil undisturbed for exactly 3 minutes without stirring.

Remove from heat and quickly stir in vanilla extract. Immediately pour the bubbling hot toffee mixture evenly over the saltine crackers, spreading gently with an offset spatula to coat every square.

Bake at 375°F for 4 to 5 minutes until vigorously bubbling across the entire pan. Remove carefully from oven and place on a wire rack.

Immediately scatter the chocolate chips evenly over the bubbling toffee. Let sit for 3 to 4 minutes to soften, then use a spatula to spread into a silky, smooth chocolate layer.

Top immediately with toasted chopped pecans, festive holiday sprinkles, and a pinch of flaky sea salt. Cool to room temperature, then chill in the refrigerator for 1 to 2 hours until completely firm. Break into jagged rustic shards and enjoy!