01 -
Heat the oven to 350°F. Line a rimmed half-sheet pan with foil, then parchment, and lightly grease the parchment.
02 -
Place the saltine crackers in a tight single layer on the pan. Break crackers as needed to fill the edges without overlapping.
03 -
Combine butter and brown sugar in a medium saucepan over medium heat. Bring to a steady boil and cook for 3 minutes, stirring often, until thick and glossy. Stir in vanilla and fine salt off the heat.
04 -
Pour the hot toffee over the crackers and spread gently with an offset spatula. Bake for 5-7 minutes, until the toffee bubbles across the whole pan.
05 -
Remove the pan from the oven and immediately scatter chocolate chips over the hot toffee. Let stand for 2 minutes, then spread the melted chocolate into an even layer.
06 -
Sprinkle pecans and flaky salt over the chocolate. Cool at room temperature for 20 minutes, then refrigerate for at least 2 hours, until firm.
07 -
Lift the chilled slab from the pan using the parchment. Break into pieces by hand or cut into squares with a heavy knife.