Step 1Wash the rice and let it soak for 30 minutes. Rinse until the water runs clear, then drain.
Step 2Put the rice and 1 cup cold water in a blender and process until the liquid becomes milky and the mixture just begins to thicken to a paste-like consistency, about 15 seconds. Set aside.
Step 3In a large, heavy-bottom saucepan, warm the milk over medium heat and add the sugar. Increase the heat to high and stir frequently with a wooden spoon until the milk mixture begins to bubble around the sides of the pan. Reduce the heat to a simmer and continue to cook for 1 minute, stirring constantly. Add the rice and cook at a very gentle simmer until the contents are thickened and the rice is al dente, 15 to 20 minutes. Be careful to stir frequently, scraping the bottom and sides of the pan so the pudding cooks evenly.
Step 4Add 1 cup boiling water, stir in the crushed cardamom seeds and rose water, and cook at a low simmer just until the water is incorporated and the pudding again thickens slightly, about 3 minutes.
Step 5Remove from the heat and divide among 6 serving bowls or glasses. Allow to cool, then refrigerate, covered, until desired. Serve sprinkled with chopped pistachios.