In a heavy bottom pan, bring the milk to a boil, stirring occasionally. Lower the heat to medium-low and simmer until the milk is about ⅓ of it's original volume. Scrape the sides of the pan, every 3~4 minutes and push the thickened cream into the milk. Don't wander too far from the milk.
Once the milk thickens, add sugar, saffron and cardamom. Simmer for about 7~8 minutes or until thickened. Turn off the heat and let cool. Serve at room temperature or chilled.
Rabri can be served as is or with gulab jamun or malpua or rasgulla.