First make the date puree. Halve dates and remove stones and stems. Cover dates with boiling water and leave to soak for about 30 minutes, until softened. Strain, reserving 6 Tbsp. of soaking water. Remove skins from dates and place them in a food processor with the reserved soaking water. Process to a smooth puree. Place the oats in a saucepan with milk, 1 1/4 cups water and salt. Bring to a boil, then reduce heat and simmer for 4-5 minutes until cooked and creamy, stirring frequently. Serve the porridge in warm serving bowls, topped with a spoonful of date puree and sprinkled with chopped pistachio nuts.