Preheat your oven to 350°F (175°C) and prepare a rimmed baking sheet. Line it with parchment paper or foil, then lightly spray it with nonstick spray. Carefully arrange the saltine crackers in a single, tight layer to form the base.

Melt the butter and brown sugar together in a saucepan over medium heat. Stir until the mixture is completely melted. Once it reaches a boil, stop stirring and let it bubble for 3–4 minutes until thickened and golden.

Stir in the vanilla extract (if using) once you remove the saucepan from heat. Immediately pour the hot toffee over the arranged crackers, ensuring it spreads evenly across the entire surface.

Bake the combination in the oven for 5–6 minutes. Watch closely until the toffee is bubbly and slightly caramelized, creating that perfect gooey texture.

Sprinkle the semi-sweet chocolate chips on top right out of the oven. Allow them to sit for about 2 minutes so they can melt. Once softened, spread the melted chocolate evenly over the toffee layer. Then, add the white chocolate chips and swirl them gently using a toothpick for a beautiful design.

Cool the pan at room temperature for about 10 minutes. Then, transfer it to the refrigerator, allowing it to set completely for at least 2 hours.

Break the chilled Christmas Crack into pieces, and serve them up! You can also store any leftovers in an airtight container for future indulgence.