Rinse the basmati rice under a lot of water and soak it in water for 30 minutes. Water should then be drained, and rice spread on a clean cloth to dry in 10-15 minutes.
The rice, after being slightly dry, is then ground in a mixer to a coarse consistency, like semolina (rava). There should not be grains of phirni crushed to a fine powder; the roughness is necessary.
Add the full-fat milk into a heavy-bottomed pan and boil it over medium heat. Reduce the fire to a simmer and leave it to simmer for 5-8 minutes until it subsides.
Warm 1/2 cup of the warm milk and combine it with the ground rice in a small bowl, creating a smooth slurry. This is what should be done so that lumps are not formed by adding rice to the hot milk.
Add the slurry of rice-milk to the boiling milk gradually, stirring all the time. Cook on low, whisking or stirring a lot to make sure that rice does not stick to the bottom or make clumps.
When the mixture becomes thick and the rice is cooked completely (approximately 15-20 minutes), add the sugar and the milk flavoured with saffron. Stir thoroughly till the sugar is dissolved, and the pudding assumes a gorgeous yellow hue.
Put in the cardamom powder and rose water. Stir it thoroughly and switch off the heat. The hot phirni may be poured into ramekins or clay bowls. Slivered nuts can be used to garnish it, allow it to cool to room temperature, and then refrigerate it at least 3-4 hours before serving.