Prepare your pan: Heat your oven to 350°F. Line a 13×18-inch (half-sheet) pan completely with foil, then line it again with parchment.
Line the bottom of the baking sheet with matzo or crackers, covering all parts in a single layer.
Make the caramel/toffee: In a medium saucepan, melt the butter and brown sugar together, and whisk it over medium heat until it begins to boil. Let it bubble for 3 more minutes, whisking the whole time. Remove from heat and add sea salt and vanilla, if using, then quickly pour it over the matzo or crackers.
Bake the caramel-covered crackers for 13 to 15 minutes, watching carefully.
Remove from oven and immediately sprinkle with chocolate chips. Let stand 5 minutes, then spread them in an even layer over the caramel. Sprinkle with toasted chopped nuts and/or sea salt if using.
Once completely cool, break or cut it into pieces and place in an airtight container.
