Warm 2 tablespoons of milk in a small bowl.
Add saffron strands. Set aside for 10 minutes.
Pour the remaining milk into a heavy pan.
Heat on medium. Stir now and then.
Add sugar to the milk.
Stir until fully dissolved.
In a separate bowl, mix cornstarch with cold milk.
Stir until smooth. No lumps.
Slowly pour the cornstarch mixture into the hot milk.
Stir constantly to avoid sticking.
Cook for 5–7 minutes.
The mixture will thicken and coat the spoon.
Add the saffron milk.
Stir gently until the color turns golden.
Turn off the heat.
Add pistachios and rose water if using.
Pour into bowls or cups.
Let cool, then chill or serve warm.