If you cannot get hold of pudding rice (it is normally found around the tinned rice pudding in the store), another short grain starchy rice will work just as well. So other options would be rices such as risotto or arborio rice, as they are short and more rounded as well as giving a wonderfully cream result!
I absolutely adore cardamom, but know it can be a bit potent for some people. My suggestion of ¼ tsp cardamom hence may be a little strong for some. This is especially true if using freshly ground cardamom, as pre ground cardamom loses its potency the longer it is stored. With all these different factors in mind, please feel free to adjust the quantity to suit your preferences.
Rinsing the rice before cooking helps the rice have the best texture and not end up a slimy mess. Soaking rice helps start the rice off on absorbing liquid, so reducing the cooking time required. You can skip the soaking if you have no time for it, but I would strongly recommend rinsing before cooking this Indian rice pudding.
As an alternative, you could use cashew nuts or even almonds instead of pistachio nuts to top this pudding. You could also add in some raisins as part of the garnish, if you wish, for extra flavour, texture and general yum!