Mix the cornflour/cornstarch and ground rice to a paste with a little of the milk.
Mix the remaining milk with the sugar and bring to the boil.
Warm the paste with a few tablespoons of the boiling milk.
Lower the heat to a simmer and, using a wooden spoon, gradually stir the warm paste into the milk.
(Be careful not to scrape the bottom of the pot with the spoon so that you do not dislodge particles of burned milk which may have occurred during boiling.) Continue stirring the mixture until it thickens enough to coat the spoon.
Stir for a further minute, then remove from the heat and stir in the rosewater or orange blossom water.
Cool slightly, pour into individual dishes and refrigerate.
Serve chilled, decorated with slivered almonds or Crystallised Flowers.