In a medium pot bring 2 cups of water to a hard boil.
Rinse the rice well under cool water until the water runs clear and add the rice to the boiling water, lower the heat to a simmer.
Cover and cook until the rice is tender and fluffy.
In a large saucepan bring the milk to a gentle boil.
If using cornstarch, dissolve it with a little of the hot milk and stir it into the pot of milk adding the rice and sugar. Boil gently until it thickens (approximately 20 minutes) stirring constantly to avoid scorching.
Remove from the heat and stir in the orange blossom water.
Pour into individual containers and refrigerate. Top with unsalted pistachios or almonds if desired.
Using cornstarch is completely optional and will simply result in a thicker pudding.