Put milk, carrots, cardamom, and saffron in a large, heavy pot, bring to a low boil, and cook, stirring occasionally, until most of the liquid has evaporated, about 45 minutes.
Add sugar and continue cooking to a pudding-like consistency.
Add the butter and cook, stirring, for another 10 minutes.
Remove from heat and fold in the cashews and almonds.
Serve warm or cold, garnished with pistachios and paneer.