In a large cooking vessel, whisk together milk, egg, sugar, semolina, cardamom, and saffron.
Cook over medium heat, making sure to stir often to prevent burning, for 20 to 30 minutes, until thickened to desired consistency. Keep in mind that the kheer will thicken as it cools.
Remove from heat and add kewra essence. Transfer to a serving dish.
Garnish with nuts. Cool completely and refrigerate. Kheer tastes best when served chilled.