Dissolve ground saffron in 1 tablespoon of boiling water and set aside (click for How to Use Saffron).
Cover a shallow 11x9-inch cookie sheet (or a shallow flat dish) with aluminum foil and pour a layer of whipping cream on the foil (about 1/4-inch thick). Place it in the freezer until it hardens, at least 3 hours.
Remove the vanilla ice cream from freezer and let it stand at room temperature for 30 minutes or until softened.
Then add the dissolved saffron, rosewater, and pistachios to softened ice cream; mix well.
Remove the whipping cream from freezer and break it into small pieces.
Add the whipping cream pieces to the ice cream mixture and stir well. Place the saffron ice cream in an airtight plastic container. Return to the freezer and let stand overnight.