Preheat your oven to 350°F (175°C) and line a 18x13-inch (or similar size) baking sheet with aluminum foil. Make sure the foil extends over the edges of the pan to prevent spillage and for easy removal.

Place the saltine crackers in a single layer on the lined baking sheet. You may need to break some crackers to fit them properly, but try to cover the entire sheet evenly.

In a medium-sized saucepan, melt the two sticks of unsalted butter and brown sugar over medium heat. Stir continuously until the mixture comes to a boil. Set a timer and allow it to boil for 3 minutes, stirring constantly, until it thickens and turns into a rich caramel color. Remove from the heat and stir in the vanilla extract.

Carefully pour the hot toffee mixture evenly over the saltine crackers. Use a spatula to spread it out, ensuring that all the crackers are coated.

Place the baking sheet in the preheated oven and bake for 5 minutes or until the toffee is bubbling and has spread out to cover the crackers.

While the toffee is baking, melt the semi-sweet chocolate chips in the microwave or using a double boiler. Stir until the chocolate is smooth and completely melted.

Once the toffee and crackers are out of the oven, wait a few minutes (about 5 mins) then pour the melted chocolate over the hot toffee. Use a spatula or the back of a spoon to spread the chocolate evenly, covering the toffee layer completely.

Sprinkle the chopped pecans or sprinkles evenly over the melted chocolate while it's still soft, so they adhere to the surface. Wait a few minutes and sprinkle with coarse sea salt if desired.

Allow the Christmas Crack to cool for about 2 hours at room temperature. Then, transfer it to the refrigerator for 1-2 hours or until it's completely set and hardened.

Once the Christmas Crack is set and firm, use a sharp knife to cut or simply break it into bite-sized pieces. Irregularly shaped pieces are part of the charm!