You could argue that this is a candy disguised as a tart, but whatever you want to call it, it is a very rich, delicious combination of buttery, chewy caramel with walnuts in a crisp short dough crust. Who could resist?
Keep a watchful eye on the caramel when you make the filling, and have the cream ready. If you let the caramel get too dark, don’t waste the cream and the butter—just start over. Not only will the filling be bitter if the caramel is overcooked, but it will set up hard enough to pull the fillings right out of your teeth! At the same time, keep in mind that if you play it too safe and do not caramelize the sugar enough, the filling will not harden sufficiently.