The history and origin of Phirni (sometimes spelt Firni) is not confirmed but often believed that the Mughals enjoyed rich milk based puddings. This milk pudding tradition is common in Persia so it is likely that the dish has origins there.
The main difference between phirni and kheer is that rice is ground in the former whereas kheer is rice pudding and you cook it whole.
50g Basmati rice
2 tablespoons water
1 litre milk