Empty contents of can into a zip-top bag. Freeze overnight. At least 20 minutes before serving, remove pineapple from freezer. Break up contents of bag. Add liqueur and ginger to blender. Add half the frozen pineapple. Cover; blend until smooth. Stir. Add remaining pineapple. Cover; blend until smooth. Stir if necessary. Spoon mixture into serving glasses. Top each with pistachios.
TIP: Add 2 tablespoons of coconut milk, cream, or half and half for creamier texture.