1. Press cold pastry over bottom and up sides of a 9-in. pie pan. Crimp edges of pie with your fingertips and prick all over bottom with a fork. Chill 30 minutes. Meanwhile, preheat oven to 375°.
2. Bake pastry on bottom rack of oven until golden brown, 20 to 30 minutes. Let cool completely.
3. Stir ice cream with rose water and cardamom until smooth. Spoon ice cream into crust, set on a plate, and freeze at least 4 hours.
4. Peel papery brown skin from pistachios with a paring knife, then put nuts in a food processor and pulse until finely ground. Sprinkle ground pistachios over pie. Serve immediately.
*Find rose water at well-stocked grocery stores and at Indian and Middle Eastern markets. In-shell pistachios are a brighter green than the type sold shelled.
More pie tips:
Let the pie soften for 5 minutes at room temp to make slicing easier.
If you're having trouble freeing your pie from its pan, set it over a bowl of hot water for a couple of minutes and then slide a thin knife between the pan edge and the crust. It should pop right out.
Make ahead: Once the pie is fully frozen through step 3, it keeps for up to 4 days, double-wrapped in plastic wrap. Top just before serving.