Nina posted the matzo toffee (affectionately called "matzo crack") around Passover, but I've been making this stuff for years at Christmas. My family's recipe is almost identical, but we've always lined the pan with saltines rather than matzo.
Saltine crackers are a little lighter, and because they're smaller than sheets of matzo, they may shift and float around a bit more once you cover them with the liquid caramel and bake it in the oven. I do like to buy saltines with salted tops, so there's an extra savory note in the sweet toffee.
My sister uses something else entirely—graham crackers. And they're perfectly delicious, too (honestly, you really can't mess this stuff up). Since the graham crackers are adding another sweet element, I'd recommend sprinkling some salty nuts on top of the chocolate as it cools.
Then there's Sara Kate's mother's toffee, which has no crunchy cracker inside at all, just buttery toffee and chocolate.
I make this toffee in the baking sheet and freeze it before I break it into pieces. Then I freeze it again. It thaws quickly (and you don't want it to get to warm or else it's messy) so I frequently take it straight from the freezer to the table or the gift bag.
Get the recipe: Chocolate Toffee Matzo Candy
(Image: Nina Callaway)