For the milk pudding, finely grind the almonds in a blender. Bring the milk to the boil – preferably in a non-stick saucepan so that the custard does not burn – and remove from the heat.
In a small bowl, whisk the rice flour with 4-5 tablespoons of water until smooth. Make sure that no lumps form. Pour the mixture into the hot milk, stirring vigorously. Cook on low heat for about 15 minutes until the cream slowly thickens. Stir constantly in one direction only so that no lumps form. (If there are still lumps, you can beat the cream again with an electric hand mixer until smooth).
Mix in the ground almonds and continue to cook, stirring regularly, on the lowest heat for 20 minutes, until the cream has the consistency of thin porridge. Then add the sugar and continue stirring until it dissolves.Stir in one direction at a time and do not scrape the bottom of the pot to prevent any burnt bits from coming off.
Finally stir in the almond essence.Let the pudding cool and pour into a glass serving bowl. Serve well chilled and sprinkled with the pistachios.