In a small saucepan, cover the nuts with water and bring to a boil. Boil for 3 minutes, then drain them and put them in a bowl. Cover with cold water, drain, return to the bowl, and cover with more cold water. Rub pistachios between your palms to remove the skins; almond skins can be squeezed off. Dry on a towel, then chop coarsely.

Whisk together the cornstarch, rice flour and 1 cup of water in a small bowl, and set aside. In a large pot, gently heat the milk until it just begins to boil. Reduce the heat, and stir in the sugar and starch. Stir up the cornstarch mix to bring up the sediment from the bottom, then gradually pour it into the simmering milk, stirring constantly. Cook and stir for 30 minutes or more, until the pudding has thickened. Turn off the heat, and stir in all but a quarter-cup of the nuts, and all of the vanilla, orange flower water or rosewater. Transfer to a serving bowl, garnish with the reserved quarter-cup of nuts, and chill for several hours before serving.