Preheat your oven to 350°F and line a 13x9 inch (33x23 cm) baking pan with parchment paper or aluminum foil. Make sure to leave some overhang for easy removal.
Arrange the saltine crackers in a single layer on the prepared baking pan. You may need to break a few crackers to make them fit evenly.
1 sleeve of saltine crackers
In a saucepan over medium heat, melt the butter and brown sugar together. Stir constantly until the mixture comes to a boil. Once it starts boiling, reduce the heat slightly and let it simmer for 3-4 minutes without stirring. The mixture should thicken and become a caramel-like sauce.
1 cup unsalted butter, 1 cup brown sugar
Carefully pour the caramel sauce over the saltine crackers, ensuring they are evenly coated. Use a spatula to spread the sauce if needed.
Place the pan in the preheated oven and bake for 5-7 minutes, or until the caramel is bubbling and slightly darkened.
Remove the pan from the oven and immediately sprinkle the chocolate chips over the hot caramel-covered crackers. Let them sit for a few minutes to soften.
2 cups semi-sweet chocolate chips
Use a spatula to spread the melted chocolate evenly over the crackers.
If desired, sprinkle the M&M's or holiday sprinkles over the melted chocolate while it's still warm.
1 cup red and green M&M's
Allow the pan to cool at room temperature for about 15 minutes. Refrigerate the pan for at least 45 minutes to an hour, or until the chocolate has set.
Once the Christmas crack is completely cooled and the chocolate is firm, use the parchment paper or foil overhang to lift it out of the pan. Place it on a cutting board and break it into bite-sized pieces.