Soak Tapioca Sago: In a bowl, add water and tapioca sago, mix well, cover and soak for 30 minutes. Then strain and set aside.
Fry Nuts and Raisins: In a wok, melt the ghee. Add sliced pistachios, almonds, and raisins. Fry until golden and set aside half for garnish.
Sauté Tapioca Sago: In the same wok, add the soaked and strained tapioca sago and sauté for 1-2 minutes.
Cook with Milk: Add milk to the wok, mix well, bring to a boil, and cook on medium flame for 10-12 minutes until tapioca sago becomes transparent.
Add Flavorings: Add saffron strands and mix well. Then add sugar, cardamom powder, and rose water. Cook on medium flame until sugar dissolves, about 2-3 minutes.
Prepare Custard Mixture: In a bowl, mix custard powder with 3-4 tablespoons of water until smooth.
Thicken Kheer: Add the dissolved custard powder to the wok, mix well, and cook on medium flame until the mixture thickens.
Add Nuts and Garnish: Add half the quantity of fried nuts into the kheer and mix well. Garnish with the reserved fried nuts. Serve warm or chilled.