This recipe goes with our Apple-Onion Tarts.
Finely grate parsnip (you will need 1/2 cup). Place on a clean kitchen towel (do not use paper towels), and squeeze to extract as much liquid as possible.
Pulse parsnip, flour, salt, sugar, pepper, butter, cheese, and rosemary in a food processor. Add yolk, and pulse to combine. With machine running, add ice water in a slow, steady stream, processing until dough just comes together (no longer than 15 seconds). Shape into a disk, and wrap in plastic. Refrigerate for at least 30 minutes (or up to 2 days).