Stir the saffron strands into the nondairy milk in a small bowl and set aside. Do this as early as possible, even a few hours before you begin to make your dish, for the best color.
Soak the cashews in ½ cup water for a few minutes, then blend into a very smooth paste. You can skip the soaking if you have a powerful blender.
Soak the basmati rice in water to cover for 30 minutes. Put a large pot of water to boil, the way you would for pasta, but don't salt it. Once the water comes to a rolling boil drain the soaked rice and add it to the boiling water. Cook for 7-8 minutes or until the rice is about 90 percent cooked. The grain should break easily between your teeth, but you should feel a bit of resistance at the center.
Once the rice is cooked, strain it immediately and spread it on a large plate for any remaining moisture to evaporate while you proceed with the recipe.
Heat the oil in a large wok or wide skillet. Add the raisins and nuts and half the cardamom and nutmeg and saute until the nuts just begin to change color.
Add the saffron and milk and the cashew cream to the skillet. Let it come to a boil, then add in the cooked rice. Mix well but use a gentle touch as you don't want the rice grains to break or clump together.
Once the rice and saffron milk have merged and there is no visible moisture in the pot, add the sugar. Stir the rice only very slightly after adding the sugar, don't merge it all completely. Cover the pot and let it all cook over medium-low heat for five minutes, undistubed.
When you open the pot most of the sugar should have melted and there will be moisture in the pot. Stir fry the rice a bit more until the visible moisture has evaporated and the sugar has glazed the rice. Again, be gentle.
Stir in the remaining cardamom, nutmeg, vanilla and rose water, if using. Turn off the heat.
Serve at room temperature or chilled. You can garnish with more nuts and coconut flakes before serving.