Adapted from recipe on Smitten Kitchen that was adapted from David Lebovitz, who adapted it from Marcy Goldman who is the genius that first applied this to matzo
approximately 40 Saltine crackers or crackers of your choice (original recipe-4 to 6 sheets matzo)
1 cup (2 sticks or 8 ounces) unsalted butter, cut into a few large pieces
1 cup packed light brown sugar
A big pinch of sea salt
1/2 teaspoon pure vanilla extract
1 1/2 cups dark chocolate chips (or semisweet chocolate if you don't like dark chocolate)
1 cup toasted chopped almonds, pecans, walnuts or a nut of your choice (optional)
Extra sea salt for sprinkling (if using Matzo)
Preheat the oven to 350°F. Line an 11-by-17-inch baking sheet completely with foil, and then line the base of the foil with parchment paper, cut to fit. (don't skip this step or your clean up will be torture)
Line the bottom of the baking sheet with crackers, covering all parts. (If using matzo, you'll need to break pieces to fit any extra spaces, which will be annoying because despite being perforated, it does not actually break in straight lines. There has been some luck pressing a serrated knife straight down along a section between perforations, if that makes sense.)
In a medium heavy-duty saucepan, melt the butter and brown sugar together, and stir it over medium heat until it begins to boil. Once it has begun boiling, let it bubble for three more minutes, stirring it well. It will thicken a bit as it cooks. Remove from the heat and add the salt and vanilla, and then quickly pour it over the crackers. You’ll want to spread it quickly, as it will begin to set as soon as it is poured.
Bake the caramel-covered crackers for 15 minutes, watching carefully as it will bubble and the corners might darken too quickly and/or burn. You can reduce the heat if you see this happening.
Remove from oven and immediately cover with chocolate chips. Let stand five minutes, they will start to melt and then spread them evenly across the caramel. An offset spatula works great here. If you’re using them, sprinkle the chocolate with toasted chopped nuts and/or sea salt. (The sea salt is great on matzo. On Saltines, it’s really not necessary.)
Once completely cool — I sometimes speed this process up in the fridge, impatient as should be expected in the face of caramel crackers :) — break it into pieces ( nibble on some) and store it in a container out of the reach of any children. (somehow it always goes missing if not hidden) It should keep for a week but it won't last that long