Add sugar, cardamom, low fat milk and saffron. Give a quick stir. Close the Instant Pot with pressure release handle to sealing. Pressure cook for 5 minutes followed by 10 minute natural pressure release.
Open the Instant Pot. Add whole milk (or low fat) and cook on sauté (normal) mode for 15 to 20 minutes or until the basundi is of desired consistency.
Enjoy warm or chilled topped with sliced pistachios.
Notes: You can add upto 1/2 cup of sugar for sweeter basundi.