Grind the almonds finely in a food processor. Bring the milk to the boil, preferably in a non-stick pan (which prevents the cream sticking and burning at the bottom), then take it off the heat.
In a small bowl, mix the ground rice to a paste with 4-5 tablespoons of water, making sure there are no lumps. Add this to the milk and cook over a low heat, stirring vigorously with a wooden spoon, and always in the same direction, for about 15 minutes or until the mixture begins to thicken. (If lumps form, you can save the cream by beating it with an electric beater.).
Add the ground almonds and continue to cook over the lowest possible heat, stirring occasionally, for 20 minutes or until the consistency is that of a thin porridge.
Add the sugar and continue to cook, until it has dissolved.
Stir in the almond essence, let the pudding cool, then pour it into a glass serving bowl or individual bowls.
Serve chilled, sprinkled with the chopped pistachios.