Preheat oven to 375ºF (190ºC). Line a jelly roll pan with aluminum foil. Spray with a nonstick cooking spray (15X10X1 inch)
Lay Saltines (30) in a single layer in a pan.
Add butter (1 cup) and brown sugar (1 cup) to a heavy-bottomed saucepan and melt over medium-high heat. Bring to a boil and cook just until it turns caramel color, about 2-3 minutes. Remove from heat and stir in vanilla (2 teaspoons) and salt (1/4 teaspoon). Pour mixture evenly over crackers.
Bake in preheated oven for 5 minutes or until mixture is bubbly. Sprinkle chocolate chips (12 ounces) evenly over top. Let sit a couple of minutes, then using an offset spatula and spread chocolate to cover. Sprinkle top with pecans (1 cup).
Let cool then refrigerate until completely cold, at least 4-6 hours. Peel away the foil and cut or break into pieces.
Notes
Don’t rush the toffee. Those 2–3 minutes of simmering the butter and brown sugar are where the magic happens. Let it come to a full, rolling boil and cook until it deepens to a caramel color—too pale and it can taste sugary instead of toffee-like, too dark and it can burn. Keep the heat at medium-high, stir occasionally, and trust your eyes as much as the clock.
Use a heavy-bottomed pan. A heavy saucepan distributes heat more evenly, which helps prevent hot spots and scorching. Thin pans can burn the sugar quickly, especially once it starts boiling. If you’ve ever had toffee seize or taste bitter, a better pot might be the fix.
Spread the toffee quickly and evenly. Once you pour the hot toffee over the Saltines, it sets fast. Use a heat-safe spatula to gently push it into the corners and cover every cracker. Any exposed cracker will be drier and less “crack-like,” and we want every bite to have that glossy caramel layer.
Let the chocolate melt on its own. Instead of microwaving the chocolate chips, let the heat of the bubbling toffee and hot pan do the work. Sprinkle the chips on, wait a couple of minutes, then spread. This gives you a silky, even chocolate layer with less risk of scorching or seizing.
Chill completely for clean breaks. Christmas crack really needs a full chill to set up—the toffee firms, the chocolate hardens, and you get those satisfyingly crisp pieces. If you try to cut it too soon, the layers can slide and smear. I like to chill it at least 4–6 hours or overnight for the cleanest shards.