Cook ada as per instructions on the pack. Drain and set aside.
Heat ghee in a large saucepan. Add the vermicelli and saute on meduim-low flame for around 5 minutes or till crisp. Ensure not to burn.
Add in the milk and give a nice stir. Cook, stirring occassionally, till the vermicelli is almost cooked.
Add the condensed milk and the cooked ada and cook till the mixture is totally thickened and the vermicelli is fully cooked.
Add in the cardamom and mix well. Serve warm.
Notes
You may temper the payasam with ghee fried cashewnuts and raisins. We did not since we ran out of both! As the payasam sits, it gets thicker. Loosen out by adding warm water to required consistency.