Wash the basmati rice and soak it in water for 2–4 hours.
Add one generous pinch of saffron to 2 tablespoons warm milk. Set aside to infuse.
Add the remaining milk to a heavy-bottomed saucepan or kadai. Lightly crush the cardamom pods and add them to the milk.
Bring the milk to a boil, then reduce the heat and simmer for 15–20 minutes, stirring occasionally so it doesn't catch at the bottom.
Continue reducing until the milk is roughly half its original volume. Remove the cardamom pods.
Drain the soaked rice and pulse it in a blender until coarsely ground. It should resemble coarse semolina. Do not grind it into a smooth paste.
Add the ground rice, sugar and saffron-infused milk to the reduced milk.
Cook over low heat for about 10 minutes, stirring regularly so the rice doesn't settle at the bottom.
Check that the rice is cooked. Continue cooking uncovered until the phirni is thick but still pourable.
Remove from the heat and let it cool slightly.
Pour into individual earthen pots, ramekins or dessert bowls.
Cover and refrigerate for at least 4 hours, preferably overnight.
Garnish with the remaining saffron, slivered almonds and pistachios before serving chilled.