Transfer the yogurt to a large bowl.
Make the saffron milk: Finely chop ⅛ teaspoon saffron threads with a knife (or use a mortar and pestle to do so). Don't worry about getting them too fine; this is just to help enhance the color. In a small bowl, add 1 tablespoon milk. Boil for 10 - 15 seconds until hot, then add the saffron and mix until the color changes to yellow - ALTERNATE quick version: simply add the saffron straight into the yogurt.
Mix: Add the saffron milk, ½ cup powdered sugar, ground cardamom, and a pinch of salt to the yogurt. Mix thoroughly until nice and smooth with a spoon -- or, for a creamier consistency, use a whisk until light and fluffy. Season to taste, adding more salt if necessary to offset the sweetness.
Chill: Transfer to a serving dish, and chill with plastic wrap for at least 4 hours in the fridge up to overnight.
Serve: About 30 minutes before serving, remove from the fridge. If needed, you can give it another whisk. To serve, garnish with 2 tablespoons chopped pistachios on top of the yogurt. Spoon into bowls, top with more pistachios, and enjoy immediately!
